Deleted

wait 7 days
marked not recieved

Mark the game as not received - not much else you can do.

The gifter has to give you the game, they made a giveaway for. You can only mark the giveaway as "received" when you get a working key for the promised giveaway.
If they don't reply to you and don't send you another key, then you can't really do something about it and will have to mark the giveaway as not received.

If he doesn't react to your attempts to contact him wait a week then mark as not received.

Usually that's not a mistake and people trying to pass of a free game as DLC. Request a valid key for the DLC or mark as not received after 7 days, and move on.

Doesnt it say what the key is for when you try to activate and click next?

Additionally to marking it "not received" after 7 days you could also file a ticket for "misleading giveaway", because it seems apparently to have been one.

what you can do is make more giveaways, not have a single one created 3 months ago.

SG sometimes doesn't show up owned DLCs as owned and still lets you enter those giveaways. Check to see if you don't you own that specific DLC already.