I also bought this game very recently and have had the same problem, I read online and a ton of people have complained and so far Playstation has said to keep trying everyday because they do not know when it will be fixed if they fix it before 3/31
Here is a link on playstation support forums http://community.us.playstation.com/t5/PlayStation-Network-Support/God-of-War-Saga-Origins-Collection-Code-Error/m-p/39756949#M28609
Definitely not the only one having the problem. I never played the origins games and figured I'd get 1 and 2 in HD. I called the phone number on the voucher was told to email them with a picture of my receipt, and the front and back of my voucher. I was told by customer service that I should hear back in 2-4 days but the automated email said 3-5 days. I really hope that they don't screw us with that 3/31/13 expiration date on the voucher.
I honestly don't know why they would put an expiration date on a voucher when they are selling the games as a 5 game bundle. They could have even had them on another disk since they are selling the origins games separately on disk format.
Playing: System Shock 2, Tomb Raider, Crysis 3 Anticipating: Gears of War: Judgement, GoW: Ascension, Bioshock: Infinite, The Last of Us