This has started happening recently. Randomly my playthrough will stop playing after a song. Pressing the play button at that point does nothing, neither does pressing the play button on any other buttons on the playlist.
There’s been some bugs in the new brainzplayer that has been ironed out the past few days (It didn’t even show itself playing on Librewolf…). I can’t guarantee that specific issue is fixed.
You may want to send a message in the Listenbrainz Discord/Matrix/IRC channel so that it get seen directly and maybe get to test it directly on your machine to make sure it’s fixed
As RustyNova said, I recently broke the ListenBrainz player by trying to fix it (a classic developer move).
I am working on a fix, but making sure to test it more thoroughly this time around…