Are you Android or Apple?

Uninstall the app. Reinstall the app and connect to your system again.

Some iOS users have complained about the same issue, and uninstall/reinstall worked for them.

Happening to me on an older Android, couple newer ones have no issues.

For a few days a device reboot fixed it but that didn’t work this time.

Haven’t tried seeing if the background process is still active and killing it, so when I get around to it I’ll do that before I try the remove and reinstall.

Edit, just tried the kill option and it failed to let it start without stopping.

@jonwhsjes 

Before reinstalling make sure to restart your smartphone. 
But first of all I also recommend a complete restart of your system including all Sonos and network devices (router, switches, wifi extenders). 

I have the same problem. I’m so tired of all this crap with Sonos. Can’t load the app, can’t play music. What’s the point in even keeping this junk.

If you removed, rebooted, reinstalled then you should call Sonos Support and have them look at the problem. They have more tools than we users do and if nothing eles you’ll get your problem on the bug list.

I have found a way that it works, shouldnt have to do it, but it does work. What you should do is disconnect your Wi-Fi from your phone and open up the Sonos app then load your Wi-Fi and it should load just fine.