Original HomePod and 2 HomePod Minis will not play together

• I’d still reboot the wifi. Even when you think it’s working in everything else.
• Restart all the HomePods as well; you can do this in the home app or unplug each one for about 10 seconds.
• Also close the music app and restart your device.
• if you want them to play on all HomePods ask Siri to “play everywhere”. Once they can accomplish this (syncing with each other), it might stick for the next time you use it.

Hope this helps.

I've been having the same issues with my HomePods/HomePods mini. I have a stereo pair of 1st gen HomePods as my default audio output from Apple TV and a HomePod mini in my kitchen and one in my bedroom. Sometimes I can get them all to play at once, but lately I've been having a lot of trouble and haven't been able to get them all to play at once from Apple TV. I can get them all to play together from my iPhone though. After well over an hour on the phone with Apple support and three different agents and multiple resets/restarts, the third guy told me that it wasn't possible to play all of my HomePods at once as they are incompatible with each other. He said that they were engineered that way for some reason that he couldn't tell me. This seems ludicrous to me, but if true, I will certainly think twice before ever purchasing an Apple product again. I'm starting to think that the days of "it just works" are over. Sad!

Same here. 4 HomePods. 5 HomePod minis. Minis all went haywire about 18 months ago. I had to unplug them. Called support twice, no fix. They are in a box in my closet now.