Please provide evidence that the key does not work. Now I see in your library of Steam games: full version of Call of Duty: Black Ops II and additional game Call of Duty: World at War. That's is all of CoD: Black Ops II Digital Deluxe.
http://imgur.com/AtGYksW
I think that support will deal with this problem and it will give you a reward for the Misuse of Giveaway Feedback.

And in addition to that, I can see your's last giveaway: https://www.steamgifts.com/giveaway/ukD2L/call-of-duty-black-ops-ii-digital-deluxe-edition
I assume you're just a scammer :^)

Reported you and added in blacklist.