I was having issues with speakers dropping from my system. When I reset them and tried to re-add them, they consistently said they could not connect to my Wifi. I tried restarting my router, factory resetting my speakers (repeatedly), connecting with an Ethernet cable (which worked but only as long as it stayed wired, which wasn’t a viable solution). I reset my app, deleted and reinstalled my app. Upgraded my system… none of it worked.

The only speakers that would connect were my old Sonos Ones—which led me to my Wifi frequencies. My router has 2.4Ghz and 5Ghz, and they are not entirely separate (you can’t turn one off and not the other). My phone automatically connects to the ‘best channel available’ which is probably the 5Ghz, and the Sonos speakers only seem to use that bandwidth for interspeaker communication.

Ultimately I did what I had resisted and gave each a unique SSID and password (sub-optimal, as it makes it so my network isn’t dynamically switchable). I was able to do this in a phone-app supplied by my internet provider. Signed onto the exclusive 2.4Ghz, SSID channel, all my speakers connected without a single problem and worked as expected.

So if you’re having similar problems it seems Sonos speakers with 5Ghz capability are not able to determine which frequency to connect to when 2 are available on the same SSID.