I had the same issue, and it seems the setup was never quite finished. I tried connecting two speakers into stereo mode. It took a long time to get them to work. I too have a mesh network, like some of you. I had to reset the speakers six or seven times until I got it right. Eventually I got it to work though.
This is what failed: setting up both speakers in stereo config using default naming in one go. The failed setup resulted in many different strange phenomena, such as just one speaker sounding, handover working with just one speaker and even sound progress bar moving on the device connected to the speakers but no sound at all playing.
What eventually worked for me was setting them up, one by one. Not adding the stereo option to begin with, but making them separate speakers. I also renamed them as separate names (homepod mini 1 and HomePod mini 2), and chose a new ew name for the room to add them to. After that was done, I joined them in stereo mode and renamed the connected pair to a third name (stereopod). The first time, joining them got stuck and never completed. I disjoined them using the setting in the home app, didn’t reset anything at that time but just tried to stereo-couple them again, and the second time it worked. They were joined in stereo mode. Handover worked to both of them. Sending audio from a Mac worked - as did all else.
Really frustrating, but I think the setup process is vulnerable to some kind of network hiccup. It waits to complete some kind of setup, handshake process, and if that is somehow disturbed, the process takes a long time or sim0ly won’t finish.
From theories in this forum, I had a look at my mesh network logs and my routers logs to make sure nothing was blocked there, which was a real possibility since I run an IPS/IDS. Nothing though. So I think it is all in the speakers and Apples chosen method of setting them up or sign off to Apples‘s servers or something. Most likely a buggy, unstable or (at least) not idiot proof enough implementation. Yet.
Hope this helps someone else.
