Relisting a game after cancelling transaction

Hi all
I sold a code to a buyer today.
The region of the code was European and the buyer did not notice it. So he received the code and after failing to redeem it, he opened a dispute and asked me to cancel the deal. I canceled the deal and he agreed to not to try to redeem it or share it with anyone, and as of now the code is still not redeemed.
Now I want to relist the game but Gameflip says that the code is already listed when I try to choose automatic delivery.
What can I do to relist this game?
Thanks

Just slightly change the entry. Add something like “thanks” at the end.

What do you mean?
You mean after I copied the code into the auto delivery box, I add “thanks” or something else after the code?

It’s checking for an exact text match so if you slightly alter the text inside the box so it’s not the exact same you will be able to relist.

Change something in the code and enter it like:

CODE: 12345-12345-12345-12345

Instead of:

12345-12345-12345-12345

Something of that sort.