In ‘Settings/System’ in the Sonos App, is your Arc now showing by it’s Room Name followed by (+LS+RS) - are there any issues/errors highlighted in the System? If not, can you rebond the surrounds back to the Arc.

With the surrounds re-bonded, if you go into the Arc room settings and choose "surround audio” if you have music playback set to ‘Ambient’ - then try changing that setting to ‘Full’ and try again and see if that fixes the issue. 

Hi Ken,

yes ive got arc showing with +LS+RS. and surround audio set to full music playback.  issue still the same unfortuantly.

Have you tried disconnecting the surrounds from the Arc and setting them back up again?

Fletchers heating,

What happens when you group the speakers the other way around - so you play music on the Arc & it’s surrounds and then go onto group the room with the Play:1 - does that work?

This sounds very like a thread I tried (and failed) to help with a couple of weeks back.  

I’m not sure the title quite identifies the issue, but I could not see anything wrong with what the OP was doing.  Unless anyone comes up with any bright ideas I think it may be best if @Fletchers heating called Sonos Support?