For the last few weeks, I have tried using the player to listen to songs on different pages (recent listens, playlists...) but it always errors. I get the following popups:

Youtube player error (2) The request contained an invalid parameter value.

Oh no ! (16) We couldn't find a matching song on any music service we tried

No more listens to play You can try loading more listens or refreshing the page

And inside the player:

You have not provided a valid SoundCloud URL. Learn more about using SoundCloud players.

It looks like it tries both YouTube and SoundCloud and doesn't work on either.

You can test with this playlist:

https://listenbrainz.org/playlist/0c109440-28d4-4495-9706-f2a54f3fe288

Or my recent listens:

https://listenbrainz.org/user/Chtfn

 Testing with Firefox 88.0.1 on Ubuntu 18.04