Fifa 21 on Xbox stopped working why?

I bought it on my Xbox Fifa 21 almost 2 months ago and was able to play it when it was released, but since yesterday I get the message when I start it: "You must have bought the game". Then I went to the store and it said that I owned it. Can someone help me or is that a bug?

Sounds like a bug if you actually bought the full version.

Delete it again completely from the hard drive and reinstall it via my games and apps.