What model router are you using?

Also, make sure the surrounds aren’t being disabled in the Sonos app:

“This light appears on home theater surrounds that have been disabled using the Sonos app.

You can re-enable your home theater surrounds in the Sonos app for iOS or Android in the  Settings tab. Under System, choose your home theater product from the list, then tap Surround Audio and re-enable the Surrounds option.”

Have you checked the LED states FAQ?

How are they showing up in your controller? Generally, surrounds will show up as +RS and +LS in the settings>system area, for the room that they’re part of.

Ah, another point would be that you can’t have the “radio” or “Wifi” turned off on either the Arc, or the surrounds, as they use that to communicate. 

Thanks for your replies. The router is a Linksys Velop and I think that’s what the problem is! I’ve checked the controller and the surrounds are enabled. They are visible as +RS, +LS. Wifi is enabled on all 3 speakers. If anyone can assist with conecting when using Linksys Velop Mesh system I would appreciate it. Thanks again.

You are sure there is nothing from the surrounds?  In the Arc settings, under surround sound, is music set to FULL or AMBIENT?  make sure it is set to FULL then play a music source, i.e. not TV.  Still nothing?

Is it practically possible - just as an experiment - to connect the Arc by Ethernet to the Router?

Thanks for your comment John B, I’ll give it a try when I get home.

I added a further comment to my post as you were replying, so please note that.  Tell us a bit more about the mesh.  Does the Velop system have a device that acts as router, or do you still use an ISP router to which the mesh connects?

Thanks again John B. It is possible that i could connect the Arc to Ethernet but I will have to lift a couple of floorboards so was going to trry that this weekend. asfar as the Linksys Velop goes it’s a normal router that has a scond router linked to it to create the mesh system I am connecting wirelessly to the main router. This post seems to highlight a lot of the problems with Velop system: Working with Linksys Velop | Sonos Community

By ‘normal’ router you mean not part of the Velop system?

Sorry, John B, No it’s the main velop router. The one I initially set up before I added the mesh node.

I am troubled by your comment ‘I am connecting wirelessly to the main router’  Does that mean you have a choice of wireless networks, main router and Velop?

Edit: posted before I saw your latest reply

OK.  I suggest the next experimental step is turn off the mesh node, assuming that the Arc can connect wirelessly to the main router.  Remove the surrounds from the Arc, and power them off and on again.  Add them again as surrounds.  Please then report back.

You don’t have any other Sonos speakers?

You should stop factory resetting as it won’t achieve anything here.

No, sorry again, my lack of understanding of this area. I have 3 wifi connections available, from my velop system. One is a 2.4 ghz, one a 5 ghz and one guest. My phone (and hence my Sonos controller is connected to the 2.4 Ghz)

Thanks for your advice John B. I’m at work at the moment so intend to crack on with it this weekend. I do have a Sonos move which works fine.

I will do as you suggest and disconnect the node.

I will also try connecting an ethernet connection to the Arc, which is what lots of peole are suggesting on other forums.

I have had my Arc for some time now and that has been faultless, it was only when I tried to connect the One SL’s that the problem started.

I’ll let you know how I get on with your suggestions. Thanks

OK.  The thing that is puzzling me is that you have the +RS+LS yet the speakers don’t appear to be enabled (green flashing light).  It may be that the Velop router is struggling to give IP addresses to the surrounds, as these get their data from the Arc by direct routing.  But that is speculative.

You could also try turning off the 5GHz band temporarily.  But only if that is easy, as I doubt very much it would help with your issue.

Please post back when you have tried a few experiments.

If you had had another Sonos speaker with an Ethernet connection I was going to suggest wiring that instead of the Arc to make the logistics of connecting easier, but the Move doesn’t have one.

Final thought - if you had said you had a non-Velop router I would have suggested trying Velop in ‘Bridge mode’.  But you don’t, so let’s hold off on that for now.

Hi John B. Ok, I disconnected the node to the router and disabled the 5ghz connection. I connected the Arc to ethernet and ensured it was selected to ethernet via the controller. I recreated the surround system via the controller and it is exactly the same. The Arc is working fine and the one SL’s are flashing green. I switched off the TV to play some music to see what effect that had and when I opened the sonos controller I got a Living Room not configured ?(+RS +LS) I had to go through the whole setup process again and, again, when I connected the surrond they flashed green. Back to the music I tried to pay musc from  my Spotify Account and Alexa said it was playing but there was no sound output (I checked the volume and it was turned up) when I checked Alexa the Arc was not visible, tried to connect it but alexa couldnt see it. 

So even the Arc won't play now?  It's beginning to look like a hardware fault  maybe with the.wireless radio on the Arc. If you just keep the Ones as separate 'rooms', not surrounds,  do they play?

Hi John B, sorry I didn't get back to you last night but tbh I was a bit frustrated with it all. I can play music through  each speaker individually if I use Spotify.  If I ask my Alexa to play music in the living room she says it's playing, but there is no sound coming out of the Arc, similarly if I ask alexa on the Arc to play music she says it's playing but there is no sound! I guess that's an Alexa thing rather than sonos. I still haven't re-tried to set up my surround as you will see from the picture below, when I added the One SL's to the system it added then as living room 2 & 3, previously all 3 were under living room.

I think you would now do best to contact Sonos Support, with the first thing to check being whether the 5GHz wireless radio on the Arc is OK. The Arc will connect to your wifi using its 2.4GHz radio then use direct routing to the surrounds using its 5GHz radio.  But anyway, I think you have tried as hard and as rationally as anyone could, and Sonos can take a remote look at your system.  You could waste hours on this yet, so I’d call.

I will also draw your attention to this thread, but I don’t really think your symptoms fit.  The flashing green lights suggest something else to me, but I could be wrong.

@HarryTheB   Your screenshot suggests you’re on a LTE network rather than local wifi? Is that right, and if so, might it have any bearing on what’s happening? Or is that the name of your wifi? 

@HarryTheB  As @nik9669a pointed out. That is a question to be answered. It looks as thought you phone is connecting to a cellular tower and Wi-Fi simultaneously. Although I’ve never seen that before. Please reply to @nik9669a question.

Thanks for your replies, definitely connected to WiFi, the lte, 3g, 4g signal shows as well.

Can you have simultaneous connections to multiple wifi networks? If so, try disabling all except the “Sonos” one. Then go through the power off everything, restart router, restart speakers process and then see how you get on with the setup. 

We know you are connected to WiFi, which is all about the LAN side of your router. LTE is about how your system connects to the Internet. Is that by a landline or mobile connection?

Maybe the LTE symbol just indicates the availability of a signal, not necessarily a connection?