A little Question

Try adding the giveaway creator on steam, if that doesn't work mark as not received after 7 days.

Thats the problem i cant see the giveaway creator cuz this message pops up

I'm assuming it was a public giveaway? If so open the URL to it while logged out or incognito and it'll ignore the blacklist screen. That way you can find who it is and add them or leave a message on Steam if they allow it as leniu said.

In case you already marked the game as received (right after viewing the key but before discovering it's a duplicate), the game shows up in your profile (click on your profile picture and then on "gifts won") and there you can see the name of the GA creator and go to his SG-profile via clicking on the name and from there to his steam account.

Otherwise what wolfedood said.

Thank you i will try when i will get home.

When winning a giveaway, there are a few things to keep in mind:

1. Do not mark the gift "Received" until it is in your Steam library.
2. If you accidentally mark the gift "Received," you are able to toggle it back off within the first couple of weeks.
3. If the gift is later revoked from your Steam library at some point, contact SG Support.
4. If you do not received the game you were promised, mark the giveaway "Not Received" after seven days.
5. If you are unable to contact the creator through Steam, you may try replying to one of his/her comments.