Since Facebook Analytics was deprecated in 2021, there was the need to create a new plugin using the Facebook SDK in order to send events.

Android: Android - App Events (facebook.com)
IOS: iOS - App Events (facebook.com)

In order to do this successfully, you require a Facebook Developer account, and an app ready to receive events: https://developers.facebook.com/apps/

Once the app is setup, replace the App ID, App Name, and Client Token variables in the Extensibility Configurations with your own. After that, and once you have dependencies to use this plugin, you should be able to generate a new app build successfully, for both Android and IOS.

In order to see the events reaching Facebook Events Manager, you need to have your app set to Live Mode. If it's in Development mode, make sure you're logged in on your phone with a Facebook user that has an App Role associated in your Facebook App.

If you do this, you should be able to see events reaching the following page: https://www.facebook.com/events_manager2/list/