Pls someone I need Help

I sold a battlefield 1 code on Gameflip and the buyer is saying that he code didn’t work so I’ve talk to Microsoft and they have said the code has been redeemed buy the person I sold it too and showed him what Microsoft said and now he isn’t confirming that the code worked when it did pls someone help me

Hey, please, can you send me your invite code via PM so I can check it for you?