unavailable

Ok, so I have four computers at my house. One for me, and each of my two brothers. We decided to buy the 4-pack of Borderlands on steam considering, we had to buy 3 anyways, why not get the 4th free.. 

So the game is up and running on 3 of the 4 PCs. I cannot get the to work on the fourth tho. it keeps saying:

"This game is currently unavailable. Please try again at another time."

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