Winner of Giveaway didnt activated 2 previous won gifts

Yes you can UNLESS he has already got suspended for that then support will be chicken robots about it and wont grant you a reroll.

You can request a new winner (do that now), but if they have already been suspended for those old wins you will still have to provide the game.

Request a new winner and see what support says.

When he or her has already served punishment your re-roll will be denied.

If he or her hasn't been punished then your re-roll will be granted and he or her will be suspended.

I see that all of your giveaways have been marked received so it seems you already sent the key. Be aware that it may have been activated elsewhere.

LOL, he's even already not activated before the game he just won from you!

sadly you have to wait 7 days and contact the support afterthat.

I recently had a non activated win, through no fault of my own. if I hadn't threatened to report the developer to Valve I'd probably still have it. Maybe you should speak with the winner before automatically judging him.