Have you tried unplugging the affected One from power for a couple of minutes and rebooting your router and phone?
Yes. I’ve unplugged all of the devices and rebooted the router and the mesh several times. Nothing seems to work.
Hello @Pdc77, I had a look on your diagnostics and was only able to find 4 Sonos One at the time you submitted. Have you tried temporarily wiring the Sonos One that is missing directly to the main router with an Ethernet cable? Allow a couple minutes for the SonosNet to activate and check the Sonos app. Can you see the missing Sonos One now? If yes, then by going to “Settings → System → Network → Manage Networks → Update Networks" while the Sonos One is still wired you can refresh the network details on the Sonos System. When that is done, you could remove the Ethernet cable and see if the Sonos One is still on your system. Unplug it afterwards and move it to its original location and you should be able to see it then. Let me know if that worked.
Thanks for the reply and I apologize for not responding sooner - was out of town for the last few weeks unexpectedly. Finally had time to try your suggestion. Connecting directly to the router via Ethernet cable does not help the situation - the missing sonos 1 is still not showing up in my system. I have resubmitted a diagnostic today (1803297902).
Hey @Pdc77 , I had a look at the new diagnostics, unfortunately still unable to find the missing Sonos One. I suggest you contact Sonos Support for a live troubleshooting, as they can help you further.