=> Someone else know that him? and history ? , he buy my code, redeemed its, then open dispute.
Code has been redeemed after he buy the code
If they open a dispute on you please send all the evidence so you can fight the dispute.
Remember to send good evidence no matter how big or small it is.
Lucy 
other customer redeemed code and open dispute
I don’t know this user, but I’ve suffered this practice: buyer buys something, uses the code and opens a dispute and then when the dispute is over (and you won), he buys the next item he wanted, uses the code and opens a dispute <= rinse and repeat. This way he tries to make you “surrender” the items to him by giving you extra work (having to upload proof of acquisition etc).
Unfortunately the only way to get rid of this is by blocking said user. You should also report him just in case he’s doing it with others, but before that be sure your code is good and it hasn’t been exposed in any ways.
It also helps if you know other people that have suffered this practice from the potential scammer, so that you point as proof when reporting him (you can find people that sell items to him on his ratings list, and then you can talk to them).
Hope it gets resolved. 
buyer use code on another 1st account, then open dispute with problem " code redeemed " with image of 2nd account
Hey guys, can you share with me via PM your invite code and order ID, so I can check this out and hel you further?
Thanks!