I looked for similar issues and employed a few solutions suggested but I don’t think they were directly related to my problem.
As briefly as possible: My system was set up in my house with a cable ISP (modem) providing internet to a Netgear Orbi router, and all was working fine with 4 Sonos devices connected to wifi. We made the decision to switch to ATT Fiber which forces us to use their Gateway box (BGW210-700) which we tried to use with the Orbi. At the time all my devices are working in the house after I switched the Orbi from router to AP mode, except for Sonos. I’ve tried router and AP reboots, resetting all my Sonos speakers and re-pairing them. Moving a Play5 speaker and direct connecting it to the Orbi via ethernet DID fix the issue for speakers (but disconnecting that speaker from ethernet kills all playback). Suggestions would be appreciated.