I have a network where there is a wireless router in my house, and then a backyard office on the same network, hard wired between the house and office, and then a wireless access point in the office. 

a number of weeks ago my Sonos system stopped detecting my Sonos system in the entire house and office when in my living room. At the same time, when in the office I could see the whole sypstem except my Living Room (Beam Gen 1, One SL’s, Sub Gen 2). 
 

There have been no changes in my router settings and I do have the latest version of the app.

I tried re-adding my Living Room, but soft reboots weren’t doing anything. I tried connecting my Beam via Ethernet, and that  didn’t do anything.

i tried a hard reboot with my beam and it was added, but it still could not detect any other devices or rooms, even when trying to add other devices in my living room. I then went to the backyard office and I could see the entire system except the Living Room Beam I just added. When going back to the house, it asked me to switch systems which I did, and then I can only see the LR Beam. 
 

Next I told the Sonos app to forget my system when in the Living Room.

Not sure what to try next? Forget every network and device and try to add all?