Buyer opening a dispute for a code I have 100% proof for

I sold a Rogue Spider Knight bundle code for Xbox One, I have proof of the code and proof that the code was not used before I sold it. After selling it to someone on Gameflip with 0 feedback, the guy just said that I did not mention the code was for Xbox only while it was written to redeem on the Microsoft website. So I checked if the code was still valid and it’s used, the guy is just trying to get his money back with bad excuses. I have provided evidence to support but I don’t really want to wait 5 days until the issue gets resolved, is there anything I can do to accelerate the process?