I'm having the same problem,. The above answer is quite unhelpful, because any restart of the Music app fixes the problem (at least for some time). So, obviously logging out or rebooting the machine is going to fix the problem, but it is not an acceptable solution, neither it provides any more troubleshooting information.
Overall, playback in Music became quite unreliable since about 11.2. I'm experiencing:
- no playback at all after wake up from sleep (can be fixed by restarting Music app)
- playback frequently stops for no apparent reason (the only solution is to skip to the next song)
- the display of currently playing song does not match the actually playing track. This usually precedes playback stopping entirely
I wished there was some easy way to report problems in the Music app, because it has gotten barely usable lately. It is now significantly more reliable to play music from my iPhone than from my MacBook. The bellow is what I get any time I want to get support for Music app (or pretty much anything else)