diff --git a/CHANGELOG.md b/CHANGELOG.md
index 870d722..d7e4577 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,7 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 * Add custom summary via shortcodes
 
-## [0.3.1] - 2024-11-16
+## [0.3.2] - 2024-12-12
 
 * Initial release on WordPress.org
 
diff --git a/README.md b/README.md
index f61876b..30f63c1 100644
--- a/README.md
+++ b/README.md
@@ -3,7 +3,7 @@
 **Tags:** events, fediverse, activitypub, calendar  
 **Requires at least:** 6.5  
 **Tested up to:** 6.7  
-**Stable tag:** 0.3.1  
+**Stable tag:** 0.3.2  
 **Requires PHP:** 7.4  
 **License:** AGPL-3.0-or-later  
 **License URI:** https://www.gnu.org/licenses/agpl-3.0.html  
diff --git a/event-bridge-for-activitypub.php b/event-bridge-for-activitypub.php
index 4bb34cf..ec9cfad 100644
--- a/event-bridge-for-activitypub.php
+++ b/event-bridge-for-activitypub.php
@@ -3,7 +3,7 @@
  * Plugin Name:  Event Bridge for ActivityPub
  * Description:  Integrating popular event plugins with the ActivityPub plugin.
  * Plugin URI:   https://event-federation.eu/
- * Version:      0.3.1.1
+ * Version:      0.3.2
  * Author:       André Menrath
  * Author URI:   https://graz.social/@linos
  * Text Domain:  event-bridge-for-activitypub
diff --git a/includes/admin/class-event-plugin-admin-notices.php b/includes/admin/class-event-plugin-admin-notices.php
index 823472e..cb4af54 100644
--- a/includes/admin/class-event-plugin-admin-notices.php
+++ b/includes/admin/class-event-plugin-admin-notices.php
@@ -69,7 +69,15 @@ class Event_Plugin_Admin_Notices {
 	 * @return void
 	 */
 	private function do_admin_notice_post_type_not_activitypub_enabled(): void {
-		$event_plugin_data       = get_plugin_data( WP_PLUGIN_DIR . '/' . $this->event_plugin::get_plugin_file() );
+		$all_plugins       = get_plugins();
+		$event_plugin_file = $this->event_plugin::get_relative_plugin_file();
+		if ( isset( $all_plugins[ $event_plugin_file ]['Name'] ) ) {
+			$event_plugin_name = $all_plugins[ $event_plugin_file ]['Name'];
+		} elseif ( isset( get_mu_plugins()[ $event_plugin_file ]['Name'] ) ) {
+			$event_plugin_name = get_mu_plugins()[ $event_plugin_file ]['Name'];
+		} else {
+			return;
+		}
 		$activitypub_plugin_data = get_plugin_data( ACTIVITYPUB_PLUGIN_FILE );
 		$notice                  = sprintf(
 			/* translators: 1: the name of the event plugin a admin notice is shown. 2: The name of the ActivityPub plugin. */
@@ -79,7 +87,7 @@ class Event_Plugin_Admin_Notices {
 				'event-bridge-for-activitypub'
 			),
 			esc_html( $activitypub_plugin_data['Name'] ),
-			esc_html( $event_plugin_data['Name'] ),
+			esc_html( $event_plugin_name ),
 			admin_url( 'options-general.php?page=activitypub&tab=settings' )
 		);
 		$allowed_html = array(
diff --git a/includes/admin/class-health-check.php b/includes/admin/class-health-check.php
index 61faa18..45d4ea0 100644
--- a/includes/admin/class-health-check.php
+++ b/includes/admin/class-health-check.php
@@ -114,7 +114,9 @@ class Health_Check {
 	 */
 	public static function get_most_recent_event_posts( $event_post_type = null, $number_of_posts = 5 ) {
 		if ( ! $event_post_type ) {
-			$event_post_type = Setup::get_instance()->get_active_event_plugins()[0]->get_post_type();
+			$active_event_plugins = Setup::get_instance()->get_active_event_plugins();
+			$active_event_plugin  = reset( $active_event_plugins );
+			$event_post_type      = $active_event_plugin->get_post_type();
 		}
 
 		$args = array(
@@ -148,7 +150,7 @@ class Health_Check {
 		$active_event_plugins = Setup::get_instance()->get_active_event_plugins();
 		$info                 = array();
 		foreach ( $active_event_plugins as $active_event_plugin ) {
-			$event_plugin_file    = $active_event_plugin->get_plugin_file();
+			$event_plugin_file    = $active_event_plugin->get_relative_plugin_file();
 			$event_plugin_data    = \get_plugin_data( $event_plugin_file );
 			$event_plugin_name    = isset( $event_plugin_data['Plugin Name'] ) ? $event_plugin_data['Plugin Name'] : 'Name not found';
 			$event_plugin_version = isset( $event_plugin_version['Plugin Version'] ) ? $event_plugin_version['Plugin Version'] : 'Version not found';
diff --git a/includes/admin/class-settings-page.php b/includes/admin/class-settings-page.php
index 3a3903f..e901064 100644
--- a/includes/admin/class-settings-page.php
+++ b/includes/admin/class-settings-page.php
@@ -97,6 +97,9 @@ class Settings_Page {
 			$tab = sanitize_key( $_GET['tab'] );
 		}
 
+		// Fallback to always re-scan active event plugins, when user visits admin area of this plugin.
+		Setup::get_instance()->redetect_active_event_plugins();
+
 		switch ( $tab ) {
 			case 'settings':
 				$plugin_setup = Setup::get_instance();
diff --git a/includes/class-setup.php b/includes/class-setup.php
index ce6afc4..f75721f 100644
--- a/includes/class-setup.php
+++ b/includes/class-setup.php
@@ -67,9 +67,8 @@ class Setup {
 		// deactivate_plugins( EVENT_BRIDGE_FOR_ACTIVITYPUB_PLUGIN_FILE );
 		// return;
 		// }.
-		$this->active_event_plugins       = self::detect_active_event_plugins();
 		$this->activitypub_plugin_version = self::get_activitypub_plugin_version();
-		$this->setup_hooks();
+		add_action( 'plugins_loaded', array( $this, 'setup_hooks' ) );
 	}
 
 	/**
@@ -106,8 +105,7 @@ class Setup {
 		if ( defined( 'ACTIVITYPUB_PLUGIN_VERSION' ) ) {
 			return constant( 'ACTIVITYPUB_PLUGIN_VERSION' );
 		}
-		$version = get_file_data( WP_PLUGIN_DIR . '/activitypub/activitypub.php', array( 'Version' ) )[0];
-		return $version ?? '0.0.0';
+		return '0.0.0';
 	}
 
 	/**
@@ -136,23 +134,47 @@ class Setup {
 		'\Event_Bridge_For_ActivityPub\Integrations\Event_Organiser',
 	);
 
+	/**
+	 * Force the re-scan for active event plugins without using the cached transient.
+	 *
+	 * @return void
+	 */
+	public function redetect_active_event_plugins(): void {
+		delete_transient( 'event_bridge_for_activitypub_active_event_plugins' );
+		$this->detect_active_event_plugins();
+	}
+
 	/**
 	 * Function that checks for supported activated event plugins.
 	 *
 	 * @return array List of supported event plugins as keys from the SUPPORTED_EVENT_PLUGINS const.
 	 */
-	public static function detect_active_event_plugins(): array {
-		$active_event_plugins = array();
+	public function detect_active_event_plugins(): array {
+		$active_event_plugins = get_transient( 'event_bridge_for_activitypub_active_event_plugins' );
 
+		if ( $active_event_plugins ) {
+			$this->active_event_plugins = $active_event_plugins;
+			return $active_event_plugins;
+		}
+
+		if ( ! function_exists( 'get_plugins' ) ) {
+			require_once ABSPATH . 'wp-admin/includes/plugin.php';
+		}
+
+		$all_plugins = array_merge( get_plugins(), get_mu_plugins() );
+
+		$active_event_plugins = array();
 		foreach ( self::EVENT_PLUGIN_CLASSES as $event_plugin_class ) {
-			if ( ! class_exists( $event_plugin_class ) || ! method_exists( $event_plugin_class, 'get_plugin_file' ) ) {
+			$event_plugin_file = call_user_func( array( $event_plugin_class, 'get_relative_plugin_file' ) );
+			if ( ! $event_plugin_file ) {
 				continue;
 			}
-			$event_plugin_file = call_user_func( array( $event_plugin_class, 'get_plugin_file' ) );
-			if ( \is_plugin_active( $event_plugin_file ) ) {
-				$active_event_plugins[] = new $event_plugin_class();
+			if ( array_key_exists( $event_plugin_file, $all_plugins ) && \is_plugin_active( $event_plugin_file ) ) {
+				$active_event_plugins[ $event_plugin_file ] = new $event_plugin_class();
 			}
 		}
+		set_transient( 'event_bridge_for_activitypub_active_event_plugins', $active_event_plugins );
+		$this->active_event_plugins = $active_event_plugins;
 		return $active_event_plugins;
 	}
 
@@ -165,9 +187,14 @@ class Setup {
 	 *
 	 * @return void
 	 */
-	protected function setup_hooks(): void {
+	public function setup_hooks(): void {
+		$this->detect_active_event_plugins();
+
 		register_activation_hook( EVENT_BRIDGE_FOR_ACTIVITYPUB_PLUGIN_FILE, array( $this, 'activate' ) );
 
+		add_action( 'activated_plugin', array( $this, 'redetect_active_event_plugins' ) );
+		add_action( 'deactivated_plugin', array( $this, 'redetect_active_event_plugins' ) );
+
 		add_action( 'admin_init', array( $this, 'do_admin_notices' ) );
 		add_action( 'admin_init', array( Settings::class, 'register_settings' ) );
 		add_action( 'admin_enqueue_scripts', array( self::class, 'enqueue_styles' ) );
@@ -303,6 +330,7 @@ class Setup {
 	 * @return void
 	 */
 	public function activate(): void {
+		$this->redetect_active_event_plugins();
 		// Don't allow plugin activation, when the ActivityPub plugin is not activated yet.
 		if ( ! $this->activitypub_plugin_is_active ) {
 			deactivate_plugins( plugin_basename( EVENT_BRIDGE_FOR_ACTIVITYPUB_PLUGIN_FILE ) );
diff --git a/includes/integrations/class-event-organiser.php b/includes/integrations/class-event-organiser.php
index 9278f43..0fbd190 100644
--- a/includes/integrations/class-event-organiser.php
+++ b/includes/integrations/class-event-organiser.php
@@ -27,7 +27,7 @@ final class Event_Organiser extends Event_Plugin {
 	 *
 	 * @return string
 	 */
-	public static function get_plugin_file(): string {
+	public static function get_relative_plugin_file(): string {
 		return 'event-organiser/event-organiser.php';
 	}
 
diff --git a/includes/integrations/class-event-plugin.php b/includes/integrations/class-event-plugin.php
index 56d020a..c5e7c40 100644
--- a/includes/integrations/class-event-plugin.php
+++ b/includes/integrations/class-event-plugin.php
@@ -24,11 +24,11 @@ defined( 'ABSPATH' ) || exit; // @codeCoverageIgnore
  */
 abstract class Event_Plugin {
 	/**
-	 * Returns the full plugin file.
+	 * Returns the plugin file relative to the plugins dir.
 	 *
 	 * @return string
 	 */
-	abstract public static function get_plugin_file(): string;
+	abstract public static function get_relative_plugin_file(): string;
 
 	/**
 	 * Returns the event post type of the plugin.
@@ -57,9 +57,9 @@ abstract class Event_Plugin {
 	 * Get the plugins name from the main plugin-file's top-level-file-comment.
 	 */
 	final public static function get_plugin_name(): string {
-		$plugin_data = get_plugin_data( WP_PLUGIN_DIR . '/' . static::get_plugin_file() );
-		if ( isset( $plugin_data['Name'] ) ) {
-			return $plugin_data['Name'];
+		$all_plugins = array_merge( get_plugins(), get_mu_plugins() );
+		if ( isset( $all_plugins[ static::get_relative_plugin_file() ]['Name'] ) ) {
+			return $all_plugins[ static::get_relative_plugin_file() ]['Name'];
 		} else {
 			return '';
 		}
diff --git a/includes/integrations/class-eventin.php b/includes/integrations/class-eventin.php
index 6ce88a6..364a2a8 100644
--- a/includes/integrations/class-eventin.php
+++ b/includes/integrations/class-eventin.php
@@ -27,7 +27,7 @@ final class Eventin extends Event_plugin {
 	 *
 	 * @return string
 	 */
-	public static function get_plugin_file(): string {
+	public static function get_relative_plugin_file(): string {
 		return 'wp-event-solution/eventin.php';
 	}
 
diff --git a/includes/integrations/class-eventprime.php b/includes/integrations/class-eventprime.php
index af78347..a50f7ff 100644
--- a/includes/integrations/class-eventprime.php
+++ b/includes/integrations/class-eventprime.php
@@ -33,7 +33,7 @@ final class EventPrime extends Event_Plugin {
 	 *
 	 * @return string
 	 */
-	public static function get_plugin_file(): string {
+	public static function get_relative_plugin_file(): string {
 		return 'eventprime-event-calendar-management/event-prime.php';
 	}
 
@@ -75,6 +75,9 @@ final class EventPrime extends Event_Plugin {
 
 	/**
 	 * Determine whether the current request is an EventPrime ActivityPub request.
+	 *
+	 * Forked from https://github.com/Automattic/wordpress-activitypub/blob/trunk/includes/functions.php
+	 * the function is_activitypub_request.
 	 */
 	private static function is_eventprime_activitypub_request() {
 		global $wp_query;
@@ -192,7 +195,7 @@ final class EventPrime extends Event_Plugin {
 		 * @see https://www.w3.org/wiki/SocialCG/ActivityPub/Primer/Authentication_Authorization#Authorized_fetch
 		 * @see https://swicg.github.io/activitypub-http-signature/#authorized-fetch
 		 */
-		if ( $activitypub_template && ACTIVITYPUB_AUTHORIZED_FETCH ) {
+		if ( $activitypub_template && defined( 'ACTIVITYPUB_AUTHORIZED_FETCH' ) && constant( 'ACTIVITYPUB_AUTHORIZED_FETCH' ) ) {
 			$verification = Signature::verify_http_signature( $_SERVER );
 			if ( \is_wp_error( $verification ) ) {
 				header( 'HTTP/1.1 401 Unauthorized' );
diff --git a/includes/integrations/class-events-manager.php b/includes/integrations/class-events-manager.php
index 2f22620..9208126 100644
--- a/includes/integrations/class-events-manager.php
+++ b/includes/integrations/class-events-manager.php
@@ -27,7 +27,7 @@ final class Events_Manager extends Event_Plugin {
 	 *
 	 * @return string
 	 */
-	public static function get_plugin_file(): string {
+	public static function get_relative_plugin_file(): string {
 		return 'events-manager/events-manager.php';
 	}
 
diff --git a/includes/integrations/class-gatherpress.php b/includes/integrations/class-gatherpress.php
index 57cd222..f68fbbc 100644
--- a/includes/integrations/class-gatherpress.php
+++ b/includes/integrations/class-gatherpress.php
@@ -27,7 +27,7 @@ final class GatherPress extends Event_Plugin {
 	 *
 	 * @return string
 	 */
-	public static function get_plugin_file(): string {
+	public static function get_relative_plugin_file(): string {
 		return 'gatherpress/gatherpress.php';
 	}
 
diff --git a/includes/integrations/class-modern-events-calendar-lite.php b/includes/integrations/class-modern-events-calendar-lite.php
index 02329ae..95bfef7 100644
--- a/includes/integrations/class-modern-events-calendar-lite.php
+++ b/includes/integrations/class-modern-events-calendar-lite.php
@@ -27,7 +27,7 @@ final class Modern_Events_Calendar_Lite extends Event_plugin {
 	 *
 	 * @return string
 	 */
-	public static function get_plugin_file(): string {
+	public static function get_relative_plugin_file(): string {
 		return 'modern-events-calendar-lite/modern-events-calendar-lite.php';
 	}
 
diff --git a/includes/integrations/class-the-events-calendar.php b/includes/integrations/class-the-events-calendar.php
index 42d295e..6f6e17b 100644
--- a/includes/integrations/class-the-events-calendar.php
+++ b/includes/integrations/class-the-events-calendar.php
@@ -27,7 +27,7 @@ final class The_Events_Calendar extends Event_plugin {
 	 *
 	 * @return string
 	 */
-	public static function get_plugin_file(): string {
+	public static function get_relative_plugin_file(): string {
 		return 'the-events-calendar/the-events-calendar.php';
 	}
 
diff --git a/includes/integrations/class-vs-event-list.php b/includes/integrations/class-vs-event-list.php
index 6ce4ba6..dc2747d 100644
--- a/includes/integrations/class-vs-event-list.php
+++ b/includes/integrations/class-vs-event-list.php
@@ -30,7 +30,7 @@ final class VS_Event_List extends Event_Plugin {
 	 *
 	 * @return string
 	 */
-	public static function get_plugin_file(): string {
+	public static function get_relative_plugin_file(): string {
 		return 'very-simple-event-list/vsel.php';
 	}
 
diff --git a/includes/integrations/class-wp-event-manager.php b/includes/integrations/class-wp-event-manager.php
index 18c217d..2adc473 100644
--- a/includes/integrations/class-wp-event-manager.php
+++ b/includes/integrations/class-wp-event-manager.php
@@ -30,7 +30,7 @@ final class WP_Event_Manager extends Event_Plugin {
 	 *
 	 * @return string
 	 */
-	public static function get_plugin_file(): string {
+	public static function get_relative_plugin_file(): string {
 		return 'wp-event-manager/wp-event-manager.php';
 	}
 
diff --git a/readme.txt b/readme.txt
index 3386f69..eb89bf1 100644
--- a/readme.txt
+++ b/readme.txt
@@ -3,7 +3,7 @@ Contributors: andremenrath
 Tags: events, fediverse, activitypub, calendar
 Requires at least: 6.5
 Tested up to: 6.7
-Stable tag: 0.3.1
+Stable tag: 0.3.2
 Requires PHP: 7.4
 License: AGPL-3.0-or-later
 License URI: https://www.gnu.org/licenses/agpl-3.0.html