Probably need more information before being able to make an intelligent diagnosis.

For instance, knowing how you’ve got the network set up might have a substantial bearing on the issue. Is one of the speakers hard wired to your router with an ethernet cable? Or does Sonos hang off your wifi? Is your wifi a single point system, or is it a mesh? Have you reviewed the wifi interference FAQ? 

Thanks. None of the speakers are hard wired all on wifi. All were on the phone app yesterday and all on the desktop app throughout. Have not changed any wifi settings. Am at a bit of a loss!

Have tried various places in the house with the phone in case there is interference but make no difference

Maybe see if toggling off/on the mobile WiFi connection will fix it. If using an iOS device, also see if disabling ‘Private Address’ (MAC spoofing) in the WiFi connection properties resolves the issue.

The issue is that none of the speakers connect to your phone for internet, so I’m going to have to assume they’re hanging off your wifi, rather than your phone, for connection. 

I suspect / my guess is that you have some sort of mesh network, and the different mesh nodes are different subnets, but the same SSID, and the Sonos system is being confused by the controller (your phone) being connected to one subnet, and the speaker being connected to the other subnet. Sonos requires all devices to be on the same subnet, in order for the appropriate “crosstalk” between not only speakers, but the speakers and the controller to work.

Try wiring one of your speakers to the base unit of your network, wait a couple of minutes, and test. 

It’s not uncommon for routers/mesh systems to do unexpected things when they update themselves in the background. Even if you didn’t “do anything”, which I do believe, it unfortunately doesn’t mean that nothing happened. 

Thanks Ken. Unfortunately no luck.

Thanks also Bruce - will probably wait until the morning rather than disturb the rest of the house!!. Assume my desktop is therefore on the same mesh as all the speakers but the phone is not. Typical!

Thanks guys for your help

Do you have a BT router by chance?

Yes

You may want to contact BT as they have acknowledged an issue with their router having issues connecting devices across their 2.4 and 5ghz frequencies.

Many thanks