I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

I did that . Not much help tbh . Just got me more confused than I was . Something to do with the tplink extender and  router on my system needing to change the name . Even though the beam system and the arc system are connected to the sky router directly by wifi . The TP link setup is for equipment without wifi .  Having just checked the ARC system in the other room , that seems to have the same problem , the sub won’t connect at all. It hasn’t been used for some time which is why I assumed it was ok . Beam system works OK after a mains cycle . Not sure what renaming a network the sonos isn’t connected to will do . It was all working fine up until a few months ago.

I recommend rebooting ARC. You may also need to reboot the SUB.

These are network issues. I’ve tried Sonosnet , but that screws up my wifi in the house to the point that nothing esle works and I lose internet connection. I can’t believe that a system that costs thousands is now apparently junk and won’t work in a perfectly normal wifi setup . 

Not sure why SonosNet “screws up my wifi in the house”? 

It may be a basic and obvious question, but are you running SonosNet and wifi on different channels? Put one on channel 1, 6 or 11 and the other on a different one of those three for best separation. 

Not on the same channels . Something to do with the Sonos connections to the network appears to be causing a loop . This is happeneing when wired or not , but is worse when wired . As soon as the Sonos is disconnected the network all works fine . 

You may be having STP issues with SonosNet. To avoid that, wire only one of your soundbars, not both. Don't wire any of the surrounds or subs.

I have tried that , but one of the two rooms still doesn’t work properly when only one of the soundbars is wired . I’ve run direct cables back to the sky hub and the network  behaves ok and the Sonos kit all works. Hopefully installing a mesh system and throwing away extenders will solve the issues . 

If so, the signal from one soundbar is not reaching well the other. This may be because of distance/obstacles or radio interference (neighbor's wifi, maybe). For the later, try changing SonosNet channel.

Thanks . I have tried all the channels with no success. The two soundbars are only 5m  apart in adjoining rooms . If the mesh solution doesn’t work I will run cables from the hub . I know that works , even if it is inconvenient to run cables.

Just to be sure, you didn't disable WiFi on the soundbar you wired, right?

I tried all the possible configurations . It could be that one of them is faulty .  I’m trying the mesh system tomorrow . If that doesn’t work I’ll do hard resets and do a full re install. Thanks for the suggestions. Much appreciated.

Whatever you try, do not turn off the WiFi on any Sonos soundbar, even if it is wired with an Ethernet cable. 

Both sound bars have wifi enabled and I ran a cat cable from the Arc directly to the sky hub.

I also had to ditch the wifi extenders . There seems to be some kind of compatibiliy issue with them and Sonosnet that caused chaos across the system.

So the Sonos systems are  now all working , but the loss of the extenders means a couple of devices on the edge of the range now don’t work well . I’m changing those for similar devices fitted with external high gain antennas . Fingers crossed that will be everything operating .

Thanks for all the suggestions.