I have an Apple TV 4K with stereo HomePods as default audio output. It is working well except that if my wife requests some music then Siri responds that Apple Music is not available. If I ask for the same music Siri will play it!
I have Personal Requests turned off so, I understand, Siri shouldn’t know who is making the request.
Software is up-to-date and the system is signed into my Apple account, which is a family subscription. It is possible that this bug appeared after I converted to the family subscription as her requests worked a few months ago.
Grrr!