The problem above is the Source Hunter DLC not activating properly with the US retail release of the game.
With the Digital Collector's Edition, there is one copy of the DLC included. Did you check with the person who redeemed the other copy of the game, to see if they got it? I would assume whoever buys the CE should get the DLC, or if it was bought as a gift, whoever redeems the first copy of the game.
Did you contact Steam support?
