Facebook Messenger isn’t making a sound when I send a message
The sound that I would normally hear when I send a message isn’t working. My notification sound when I receive one is working just fine.
iPhone 13 Pro Max, iOS 15
The sound that I would normally hear when I send a message isn’t working. My notification sound when I receive one is working just fine.
iPhone 13 Pro Max, iOS 15
Facebook is not made by Apple, so we cannot help you here. You'll need to contact Facebook.
If you don't see notifications for a specific app
To get notifications, connect to a Wi-Fi or cellular network. If you still don't get notifications for a specific app, try these steps:

Change notification settings on iPhone
Facebook is not made by Apple, so we cannot help you here. You'll need to contact Facebook.
Facebook Messenger isn’t making a sound when I send a message