My Beam and 2 x Ones disconnected from router today out of the blue. 
Took well over an hour of Ethernet connecting/ disconnecting and setting up system to receive wirelessly from router. 
Worked for short while then disconnected again. 
Currently working but not sure for how long. 

Hi @mewantsonos and @electrosim2001.

Thanks for reaching out.

We would like to look into this more, but we’ll need some more details to look into it better.

Kindly please submit a diagnostic report through the Sonos app, and reply with the confirmation number.

It can help up identify what is causing your issue.

I am looking forward to assisting you further from here.
If you have any other questions or run into any issues, please do not hesitate to reach out.

I got this issue yesterday where my Left Surrount ONE SL disconnected from the ARC+SUB group. I unplugged and re-plugged it, didn't connect automatically. Followed the instructions within the app and repaired it with the group. However there was no sound from it. I had sound in Right surround but nothing in left. Athough the speaker showed connected to the group, there was no sound. Then I ungrouped the entire setup and speakers. Regrouped them again and added the surrounds and sub. It fixed the issue for me. Try removing your speakers from the group and set them up as individual. Then add them to the group. This may work for you.

Dear sonos team. 

this is a recurring problem for me as well. my setup is arc + sub + 2 one sl. the arc is wired to an access point. on the app on the system tab the sub and both rear surround shows the ? symbol. i’ve submit a diagnostic confirmation no 1484303095. if somebody can give a solution would be much appreciated. thank you.

best regard

m. zainuddin

Power cycle should fix the issue at least it fixed mine.