Settings → System → (Ray room) → Surround Audio

I see two settings tv volume and music volume … the music volume increases the PLay: 1s volume, so that does the job for me. Strangely the TV volume does nothing

If there’s no surround signal being sent to the Play:1’s there’s nothing to hear. Make sure an appropriate “effect” sound is playing and then try. 

Don’t know what you mean by ‘effect sound’ - i bought the bar for tv surround sound, the TV supports surround sound, 2 PLAY: 1s and Ray are setup as surorund sound, plugged into digital out but no joy

A lot of TV content, particularly news broadcasts, contains little if any surround information. Try streaming content; basically anything claiming to actually be in 5.1.

Clearly the surrounds are connected and working, as music plays.

Ok, I’ll check - The TV’s been for a couple of hours and we haven’t had any sound through the two Play: 1’s so far

You can inspect the actual content format in the Sonos controller app. On the Now Playing display for that room it will list the encoding. If it says ‘stereo PCM’ -- or even Dolby 2.0 -- then there’s no surround information in the input stream, so Sonos has to synthesise something suitable to send to the surround channels. As I say, with a lot of broadcast TV this doesn’t amount to much.

Try a Netflix, Amazon Prime, or a Disney+ movie perhaps and ensure the TV is set to output Dolby Digital 5.1 audio (and not DD+ or PCM stereo)