Have you tried deleting the app and re-installing? I know you shouldn’t have to and the ‘quality’ of the Sonos App is getting more than a little tiring, but it might be the quickest resolution before taking the plunge with Sonos support. 

Hi Keith. My app does exactly the same but only on the Android & never on the IPhone. I always unplug the router wait a minute & then it works sometimes just switching the phone off does it. I know this is not a perfect situation & I agree with what you are saying, but if you haven’t already tried this might be worth it. Good luck

Thanks both - I have just spoken to Support and they asked me to do what you have suggested, ie delete and install the new app, unplug the router and all my speakers and re-plug them in.  It seems to be working now. 

Another day - another complete failure of the App - all I get is “no connections found “ and I can’t play anything or see any speakers 

this has all come about after the update at the end of last month 

Sorry you are having hell again Keith, try switching phone off then back on, unplug router (I know again) if that doesn't work, leave it a couple of hours or so & try again. Good luck mate