Homepod minis won't work as stereo speakers with Apple TV

Hi cedarhorse,

To use both HomePod mini speakers with your home theater, you must follow the instructions outlined in the article that you viewed prior to posting here:

"Set up home theater audio

1. Assign your Apple TV and HomePod or HomePod mini to the same room in the Home app. If you want to use two HomePod or two HomePod mini speakers, create a stereo pair, then assign the stereo pair to the same room as your Apple TV in the Home app.
2. Turn on your Apple TV. You'll be asked if you want to Use HomePod speakers as Apple TV speakers. 
3. Select Use as TV Speakers to turn on home theater audio. 

"

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

If you have followed those instructions and still can't get it working, contacting Apple Support is the best path forward to resolve this. They will be best equipped to investigate this further for you:

Get Support

Cheers!