You can try “resetting” the app first: Tap on the account icon at the top of the home screen, then tap app preferences, scroll down and tap reset app.

You can reconnect to your system afterwards.

If that doesn't work, you can then try uninstalling and reinstalling. This is just for the app, so the system will stay intact so that you can then reconnect after the process.

The app is just a remote to the system, where all settings are stored.

I do mostly Android but I’ve cleared a couple issues by rebooting my controller’s device.

If none of that works power down all but one Sonos, wire it to Ethernet and try the update again, if it works then try powering up the others and updating them.

Thanks all. I deleted the app and reloaded and that allows the update to succeed ….although now although I can see all the units in the app they’re not connecting to the app.! One thing I’ve never been sure of is if when I disconnect everything (units and router) what should I connect back up again first, the router or the units…..or doesn’t it matter? By the way I have a Port hardwired in with an ethernet cable and the rest on WiFi.

Usually power up the router, then the wired Sonos. Otherwise do the Sonos closest to the router first.

If you have a wired Sonos it is unlikely that your other SonosNet capable Sonos are connecting to WiFi instead of it. There is an option to disable that but it is best avoided unless you have good reason to do so, calling Sonos first is recommended.