Send key or request new winner? [SOLVED]

Your reroll request would be denied. To instigate a reroll, the user would need to be invalid for entry (no longer part of the group or of the right minimum level), would need to be suspended (meaning if you can find a non-activated game or multi-win they haven't previously been suspended for, you can link to that information within your reroll request), or would need to already own the game in question.

If the user hasn't opened themselves up to issue in the first place, then there's no basis for withholding a win from them. That is to say, by site rules you're obligated to send the game and, excepting for packages where they already own a majority of the content [and even there, it's expected you'd list any expectations related to that in the giveaway description while the giveaway is active], users are not allowed to reroll on winners at their own discretion.

If you're concerned with users winning too much, then blacklist winners and start each giveaway only after the previous one has ended. Or, create your own single-win group, and eject someone after they've won once.

Send the key. User was lucky. Others aren't (-6 gifts this month for me). Things work like that. In the long term, everyone should have more or less the same luck so no big deal.

Send the key. This is an accident, it happens.
A few years ago, before I deleted my old Steamgifts account, I had a funny case - I won the same game with a difference of 5 minutes. These were private and public giveaways in which there were many who entered, but it coincided.