Missing Notifications when following exoplayer migration guide.

I have been attempting to convert my app from exoplayer to media3, and using the migration guide here:

https://developer.android.com/guide/topics/media/media3/getting-started/migration-guide

It's been going reasonably well (despite all the examples and documentation being in Kotlin, and my app and knowledge soundly in Java). I have my streaming radio player app compiling and working. It's really only the notifications I need to get working. Currently my app doesn't show show media notification,

The migration guide states:

The MediaLibraryService supports media notifications automatically and the PlayerNotificationManager can be removed when using a MediaLibraryService or MediaSessionService.

This is not the case for me, and I'm not entirely sure what's going on. As with Exoplayer, the service/notification/session interactions are all very confusing and constantly changing.

Here is my service.

https://pastebin.com/MiK9Misj

Any pointers or clarifications on the migration guide would be appreciated.