Apple TV 4K Box and HomePod Mini connection issues

For default audio, the HomePod speakers and the Apple TV box should be assigned to the same named HomeKit room. Did you set it up like that in the Home app on iPhone or iPad?

Set up accessories with Home on iPhone - Apple Support

You will not tap into surround sound audio from HomePod mini speakers. They can be configured as a stereo pair at most.

For surround sound and Dolby Atmos processing, you’ll need the larger HomePod speakers.

Set up home theater audio with HomePod or HomePod mini and Apple TV 4K - Apple Support

I am having a similar issue. Mine keeps telling me that it can’t make HomePod the default audio output and then disconnects. I select it again and it works for a while then does it again. This only started after the last update. I have used a HomePod stereo pair as default audio for years, including the second generation HomePods since they were introduced. I even upgraded to the latest Apple TV and still have the issue.

If it doesn’t work as it is described that it should, when you’ve done everything right, then please contact the Apple Support staff for assistance and/​or reporting something that needs to be fixed.