Hi, Knedlik!
My name is Caio and I'll be happy to help you today =)
Have you ever been a GamePass Ultimate (or PC only or Xbox only) subscriber?
Because, depending on this offer terms and conditions, it might be only eligible if you meet this criteria. It's a common prerequisite on GamePass deals.
When he bought it, didn't the card/email have any "fine print" on it?
I hope this helps you! Please let me know if I can assist you more.
Best regards,
Caio G.
Independent Advisor