Does the app have the right to connect to devices via wifi?

Thanks for your answer.

I don't see what would prevent SONOS S2 from NOT being able to connect via WIFI. It worked for my BLACKVIEW table.
My phone is on wifi.
It's beyond comprehension. It worked with my old phone.

I don’t understand ….

If the Sonos app didn’t ask for -- or wasn’t allowed -- various permissions, including location. that’s likely to be your problem. Press and hold the app icon then choose “i” from the popup and check the permissions. You can always start again by force stopping the app then hit Storage and Clear Data.

Storage and Erase data operations done.
I checked that SONOS S2 was correctly set up for WIFI. Everything's OK. I set SONOS to WIFI only.
Unfortunately, I still have "
Connect this mobile device to the WIFI network to continue."
I have version 15.10 - 01-31 Dec.
Nothing, still NOTHING!
Impossible to go to the next step.

Does Sonos ask for any permissions when it starts afresh?

Do you have a VPN installed/active on the phone?