Xbox Game Pass App is not working?

https://www.playcentral.de/spiele-news/xbox-game-pass/pc-so-ladet-ihr-neue-windows-10-app-herunter-id78666.html

According to this page one should simply load and install the app. But with me comes the message (picture)

My Windows is up to date, someone a solution because the game pass is so cheap for just a few days and I want to test it.

As far as I know the developer mode must be activated in the Windows settings, or you have to be an insider (it was said in MS), but on the other hand I do not believe that.