I’d kill the app on the iPhone, then restart it. Frankly, I’d likely delete it after killing it, then download and install a fresh copy from the iOS store, making sure to ‘Connect to existing system’ when asked during the install process, just in case the original install got corrupted in some way during the download process. Perhaps a bit paranoid, sure, but being able to do a fresh install of an app is reassuring to me. 
 

For what it’s worth, I run most frequently on an iPhone, and two iPads, and haven’t had an issue yet. 

I don’t know how to kill the App, so I deleted and re-loaded the SONOS App which sorted the problem out. I had considered this option but balked when presented with a number of download options on the IOS store.

The “Connect to existing system” seemed to work, linking to my router although when selecting my system it requested me to connect my One SL via Ethernet. This I cancelled, instead selecting access at the bottom of the App screen, which reactivated my radio connection on the speakers.

Many thanks for responding to my request for assistance.

https://support.apple.com/guide/iphone/quit-and-reopen-an-app-iph83bfec492/ios#:~:text=To%20quit%20the%20app%2C%20open,)%2C%20then%20tap%20the%20app.

Thanks

There is a lot I could raise with you, but I guess the best thing to do is wait until SONOS start releasing fixes.

Regards, Peter X

Why with me? Raise them with Sonos instead, by calling Sonos Support directly to discuss your concerns.