Perhaps a DHCP Server issue with your router. See if reserving all your Sonos devices IP addresses in the DHCP Reservation table fixes the matter for you.

Hi Ken, 

Thanks for the response and suggestion. I just gave that a try and then restarted the router but the problem reoccurred. Do you have any other ideas?

thanks 

Spencer 

Does it work if you perhaps cable ‘just one’ sonos device to your router?

Well, the router is in a room where I don’t keep any of my Sonos devices. Do you recommend this as a troubleshooting step or as potentially a lasting solution?

No just a temporary measure, to see if it resolves the issue. Is it a wireless ‘mesh’ system you are using by any chance, with satellite hubs/access points? If so, which mesh system is it?

If you have other access points in the home besides the main router, then ensure they are all set to the exact same WiFi credentials (SSID/Password) as your main router. Use the same non-overlapping channels (1, 6 or 11) on all access points for the 2.4ghz band and use the same channels for 5ghz band too (whichever channels you choose) and fix them, rather than allowing any of your devices to auto-seek a channel. I recommend a channel width of 20MHz for your 2.4ghz band and 40MHz width for your 5ghz band.

When wiring a sonos device to the main router, ensure to set the SonosNet channel in the Sonos App ‘Settings/System/Network’ to a channel that is at least 5 channels away from the routers 2.4ghz channel. That will help reduce interference. 

Keep your Sonos devices at least 3 feet away from any other wireless device (if practicable) particularly keep any wired sonos device away from the router to help improve communication.

Then see how that works for you, but give the system a chance to settle - at least half an hour, before testing a full reboot of the system.

Ken!

I think you solved it. Wiring a device definitely helped for the group that the device was associated with but not for a different group. But designating a router 2.4 channel at least 5 away from the SonosNet channel seems to have fixed it. I’ve tried numerous reboots and all Sonos groups are found and reconnected right away.

thanks so much. This has been driving me nuts for months.

Spencer