I searched a little further, it seems related to this issue.: Music rating doesn't work in latest Plex versions
Apparently, the bug appears with basic music libraries. I checked my setting and I probably created a basic music library. Trying to recreate the music library, I noticed that I cannot create a Plex Premium Music library, while I have a valid Plex pass.
And then I looked a little further and noticed this message: Important information regarding Premium Music libraries in Plex
Seems that I have to wait for a while.
