Premium music libraries are changing. AFAIK, everyone should have received an email notification to this effect.
To copy the answer from there and close this thread.
“I fixed it by logout from my plex media server on my server PC and claimed it again.”
Plex changed its metadata provider (all this should be in the notification email)
Sign out / back in, updates the server.
PMS 1.16.1 and above will be required for Premium music.
