Bought Xbox Game Pass Ultimate but not working?

I tried to redeem a code for Game Pass Ultimate. It didn't work the first time. When I re-entered the code, the message came that the code had already been redeemed. But this was not true.

I then redeemed the code again, but the message came back that it had already been redeemed. I then restarted the Xbox, but it didn't work either.

My uncle bought the pass again afterwards. But again it didn't work.

I've already looked on the Internet, but haven't found anything.

Has anyone ever had this problem and / or can I help?

Where did you get the code from?