I have the same problem rubbish 

Seems odd that as the OP, you have the ‘same’ problem. Isn’t it just the one problem?

Which PLAY:5 do you have, the first generation, or the second? The first generation can only be used with the S1 app, downloaded from the appropriate store, and used with other speakers running the same OS. The second generation, of which I have a pair, run on either S1 or S2. I run mine on S2, using the latest controller, downloaded from the Apple Store (iOS in this case, for the S2 Mac/PC controller, it isn’t in the various stores, it is available directly from Sonos on their website). 

I’ve never seen the S2 controller ‘tell’ me to downgrade, so I’m curious about that. Have you tried a call to Sonos Support directly to discuss it?

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.