You are probably setup under another email.  See this link:

https://support.sonos.com/en-us/article/transfer-your-sonos-system-to-a-new-account

Thanks but it asked me to logon and it fails.

that is the problem to being with.

As @jgatie said you are probably using a diffrent email. Did you or someone else setup your Sonos or did you obtain thew Sonos components from someone else (i.e used system)?

No, I’m the only one. How can I logon to the website and not to the App?

thanks for the help 

Because they can be different. I have five Sonos systems, spread across three Sonos accounts. Only one of them is used to login to this forum and the web site.

Also: forum login != web site login I believe, though its been a while.