Every damn key...

My guess would be because Steam is, by law, not allowed to do business in your county (Syria?).
I could be wrong, and if someone is willing to elaborate on what I'm trying to say here, go for it.

Looks like some games are not available for purchase in your country

Have you contacted Steam support?

Are you able to purchase stuff in the steam store normally?

So they want your oil and your money, giving nothing in return... damn:D

Same thing happened with one of my giveaway winners. I contacted Indie Gala, since that's where I bought the game from, they said they'll contact steam support to see what the issue is, but nothing so far. It's been about 2 months, and giveaway winner does not care to contact support himself, so I pretty much accepted that this giveaway will be marked as not received.

In that case, shouldn't you tell the giveaway creator to re-roll rather than mark it as not received, since it's obviously not the giveaway creator's fault that you cannot redeem the key?

Of course, there's the fact that the giveaway creator can't make sure you haven't given the key to someone else. Not sure how you should proceed in that case... maybe contact the SG support through a ticket to explain it?
I just think it would suck if the giveaway creator would get a negative giveaway feedback when they aren't the cause of the issue.

Steam blocked keys activation in some Middle East countries !

There was another Syrian guy who made a thread a month or two back and had the same problem. Steam is not going do business with you currently at the sayso of the US government.

From what I remember he tried VPNing some steam wallet and even that got locked.

You might want to stop entering giveaways.

Edit: http://www.steamgifts.com/discussion/MrAlI/cant-redeem-retail-keys-anymore - there's the thread I remembered.

Double edit: It was actually this one, or a combo of the two - http://www.steamgifts.com/discussion/2yZMH/lost-all-hope-in-steam-this-is-injustice-update-still-locked/search?page=3

There was another guy from Syria not long ago who complaind about the same thing
sadly i don't think you can fix it...

Had it recently with a ROW copy of Sleeping Dogs i won here, trying to activate the key in german steam always resulted in the error from your image. I checked steam.db, found out Sleeping Dogs was removed from store, assumed that was the culprit - and shrugged it off as bad luck.

Maybe try writing a message to steam support? You will get official statement.

Or you can try using VPN. I nvere did that, so I don't know how to do this, but I heard other people did that. But before considering it, check if it's safe to use in your country and all, I don't want you to have problems because of me.

I got the same error trying to activate the game Risen 3 I won a couple of months ago. It was the only time I encountered this error though. I never had any issues trying to activate keys on Steam. The giveaway creator was surprised, because the key wasn't supposed to have any region restrictions and he gave similar keys from the same batch in previous giveaways, all without issue.

It's a shame the use of VPN's and proxies is frowned upon even in a case such as this, wherein the restrictions aren't for monetary reasons, or tax reasons, but almost wholly political, and driven by censorship. Those are the people who benefit most from such services. But I do understand the need for such restrictions (Steam's anti-vpn stance, not draconian censorship laws).

Its probably because of your country. Steam is not allowing any transactions from there and you have to suffer for that.

Contact Steam support immediately.

May god bless you and your country.