We also have an English speaking community. 
https://en.community.sonos.com/search/activity/recent

I suppose your Android Version is not up to date for newest Sonos app. 

Thank you, but completely up to date

What device and Android version do you use?

Did you try to install Sonos app from Google playstore?

Hello, and thank you for the replies. Turns out that it was the stupid phone! After multiple restarts, cache clearings, etc. I finally persuaded the app to load, and from that point on it was relatively plain sailing, and we are up and running.

I just wish that people would devise systems that didn’t require a degree in computer science. Or a substantial slice of clairvoyance. “Go to menu X, click on item Y”. But what happens when item Y actually isn’t there? One then has to go off on a treasure hunt. Perhaps it’s a function of age (I’m 75) and I come from a time when one simply wired things together and they worked.