Problem adding surrounds to Beam

@iancooper7, have you perhaps tried power-cycling the Beam and fully closing/reopening the Sonos App to see if that fixes the issue?

While you wait for a Sonos rep to look at your diagnostic, I’d try two things. 

First, check your Beam to be sure that the radio/WiFi hasn’t been turned off in the room’s settings. It should be ON. 

Second, unplug all Sonos devices from power, and while they’re unplugged, reboot your router. Once the comes back up, after a minute or so, plug the Sonos back in, wait a couple of minutes, then try to re-add the surrounds.

If neither of those potentials solve the issue, it might be helpful to know the make and model of your router, too. 

Ok, I tried to do what you suggested, but the same thing is still happening. My router is a Netgear Nighthawk MR60 mesh with one MS60 satellite.

If your router has ‘QOS’ enabled, then see if switching that off resolves the matter.

QOS hasn't been enabled. I thought maybe one of the speakers may be trying to connect to my satellite instead of my main router, thus causing the weird desync, but I'm not 100% sure it is.

In a bonded Sonos HT setup the wireless ‘surrounds’ connect directly to the main Sonos HT device (the Beam in this case) using an ad hoc 5Ghz connection - they are each controlled by the Beam and are effectively slaves to that device. It’s the link between the devices that is the issue, hence Bruce’s question asking if you may have switched off their radios, but sometimes external things, like QoS, or network multicasting, can get in the way of things.

I would next try wiring your Beam, or another Sonos device direct to your main router, but do not use the surrounds as a wired device, if that is practicable to do with your system?

It shouldn’t. When they change from ‘normal’ speakers to ‘surround’ speakers, they also switch from your WiFi normal  signal to a 5Ghz signal generated by your Beam. Which is why I asked you to check that the radio on the Beam has not been turned off. 

I had the same problem. I have one Arc + sub and have had two Play 1 as surround speakers for a long time. But those two just stoped working. I removed them and installed them again and as soon as I try to add them as surround it’s not working. Same error as mention in this thread. I also use mesh network but have been doing that all the time. Anyway, I got it to work again by connection my Arc with ethernet cable instead of wifi. Then added those two Play 1 again and it’s working.

So, what has changed? Software update? Why do I have to use the Arc with cable to add those two Play 1 as surround speakers? I haven’t change anything else.

Most likely a change in the firmware of the router. I would suspect the newer version  isn’t ‘happy’ with the concept of proxied IP addresses while on strictly wireless, but that’s a guess, of course. It’s the only logical explanation for why it would work while wired and not wireless, to my knowledge. But the surrounds are connecting to the Arc first, not your wireless signal, so the Arc has to get proxied IP addresses from the router that it then hands off to them. 

Restart your network. 
 

I had this same issue with both beam + Symfonisk  speakers and Arc + Ones. Restarted network and boom, all is back to normal.