I got code doesn't work

Re-read GA text. Leave comment for author?

Do not mark as received. Attempt to contact the ga creator and explain the situation. If they respond, there's typically one of 3 possible outcomes. They may try to replace the key, they might acknowledge it was an older key (or couldn't remember if it had already been used) and ask your approval to delete the ga, or they might ask support to look into the situation if they suspect foul play was involved. (There are other outcomes, but these 3 seems to be the most common)

If they don't respond or the situation never gets handled, you can mark the game as Not Received after 1 week from the end of the ga. If it is still marked Not Received after 30 days, it will remain on their stats forever. At that point only Support can change it, but would need a very good reason to do so.