Won a giveaway and the received key is not valid, what to do? THZ

Keep calm and

Contact the support and explain everything.

Report the heck outta the giveaway creator

Contact the GA creator and let them know...it could be a misunderstanding.

If they will not work it out, then report them.

Dude, I got "Call of Duty Black Ops 2" (6033 at the raffle), a week ago, and the donator ignores me xD

You are not the one.

It might be region locked, if so, blame it on valve.

Talk to the creator, if he refuses to give you a valid one, mark as not received after 7 days.

Buy the game yourself, activate it, mark as received.

Don't forget to tell ga creator to mark 'gift sent' checkbox.