Default audio not working with HomePod mini's
I have an Apple TV 4K (2nd gen), x2 Home Pod Minis. They're brand new, and updated to OS15. When I try and set the minis, which are a stereo pair, as the default audio it just loses sound. I try and adjust the volume using the remote and it doesn't work anymore. The onscreen graphic is no longer the thick volume bar with a pair of homepods in it, it's a thin white bar and it doesn't change the volume, the bar doesn't move. And sometimes it's even the TV volume indicator instead. Nothing I do seems to work getting sound to come out when I set the Homepods as the default audio. I have tried restarting, both devices. nothing works.
Anyone else had this issue? Any ideas on fixing it.
I specifically bought this setup to use with my LG C1 TV and Xbox Series X using HDMI eARC - but I can't even get audio to work with the Apple TV.
Apple TV 4K, tvOS 15