I installed Grounded from xbox game pass. when I clic on "play", the game open but It stays in "signing in... ". I found that if you put it on full screen you can login "manually" but I can't put in in full screen either.  

I'm having the same issue, just get stuck in an infinite loop of signing in, it recognizes my account I click "Let's Go" and I can see for half a second that the login pops back up before it shows the main menu, if I click multiplayer it goes to the login screen again.  glad I wasted the 4 hours I get between work and sleep on not being able to solve this.