Hi @GUPA
Welcome to the Sonos Community!
Sorry to hear of this issue you are having with signing in to the Sonos app.
The reason you are having so much trouble is that there is no system registered to the account with which you are signed in here at the Community - if you are using the same log-in details in the Sonos app, it is the wrong set of credentials to use.
If you have another Sonos account, I recommend you try that instead.
Otherwise, I recommend you first log out of the Sonos app: User Icon » Sign Out.
Then, transfer ownership of your system to the account you are using here: Settings Icon » General Settings » Transfer System Ownership.
I hope this helps.