Key Recipiant doesn't acitvate key, nor mark the gift as Received, nor answers any inquiries

I'd suggest sending a ticket to Support, along with your proof. Have you checked his account to see if the game is on it?

Ask support for a reroll.

i have the same issue i do not see it on his account and when i check the link it does not tell me the key has already been used though i have not checked lately

i will give it another day or so and try contact them and then maybe put in for re-roll as the point of me giving the game away was for someone that will active it i bet the person entered just because he could this is why i sill think the points system is still a bit broken as some enter stuff they normally would not just for the heck of it and win a game they have no interest in

Check users steam name and aliases, find his matching account on gameminer. See your game in a GA under his on gameminer - submit report here.

This happened to me as well. I contacted support and sent them proof that I have given the gift. Support manually marked it as received and dealt with that annoying winner.

Happened to me once, I requested and got a reroll on support's advice to do so.

New winner activated key with no problems.

I presume if the key turned up as used already, Support would have marked the gift as Received and we'd just have to apologize to the second winner.