It might be that your area has not been given access to the latest update, that can take several days depending on your luck.

I’d call Sonos Support and ask them if they can tweak the update process for you.

There are two kinds of updates: app updates and speakers’ firmware updates. When you tap on Check for Updates in the app, it'll update the speakers’ firmware. To update the app you have to check either Google or Apple stores, and as @Stanley_4 mentioned it's been rolled out gradually.

Thank you, after a few attempts managed to get the app updated and all working now