Can't sign in to Xbox Live (Windows 10)?

Hi! I bought the Xbox Game Pass a few days ago. Then I downloaded Sea of Thieves and of course wanted to play it directly. When I started it, of course it wanted to connect to Xbox Live, but it couldn't connect even though I had an internet connection. I've already googled but found nothing. Just saw a couple talk about this Xbox app. I downloaded it and there the same problem, only weirder. Because every time I press "Register" I can register, but if I then press "Play Now" I get to the start page and I was not registered.

How does something like that and more importantly: how do I fix something?

Please contact XBOX Support.

https://beta.support.xbox.com/