"More than one device is trying to play music."

alforkosh wrote:

I am getting the message "More than one device is trying to play music." in the Music app on my Mac once or twice a day. I am playing from the Music app on my iMac and also have the output directed to my stereo HomePod setup in another room. All the devices are registered to the same AppleID (mine) and there is no other AppleID involved. So the Family Sharing suggestion that appears is irrelevant. For what it's worth, I most often see the message just before midnight (PST).

Your individual Apple Music subscription allows you to sync your iCloud Music Library to multiple devices but only stream to one device at a time.

alforkosh wrote:

I don't believe that is the problem. When the HomePods are used as Airplay speakers, they are not independent devices, but controlled by the Mac. The Music app allows output to multiple devices at the same time. Furthermore, playback may pause (sometimes it does--sometimes it doesn't). However, even when paused it can be resumed after clearing the message.

well... that's what the message means, so "it" believes 2 streams are playing.

Suggest calling support - https://support.apple.com/contact