I recently bought Dead Space 3 for PS3, brand new, and I can't redeem my code.
Within the game, I get a message saying that "Downloadable content is not available at this moment", and the redeem option is grayed out (can't even enter the number). When I try through PSN->Account Management->Redeem codes, or through Origin, I get a message saying that the code was not valid.
But the game was new.
After trying to call by phone, then waiting for more than an hour to chat with someone in customer service, then spending an hour following some steps that didn't actually help, I kept trying and managed to redeem the code.
I bought the game in the UK, where I live now, but I bought and used my ps3 in the US before. So I created a new user on my ps3, linked that user to a new PSN account I just created, making sure its region was set to the UK, and then was able to redeem the code.
I also tried to copy my saved data to this new user account, so I could resume my 16 hour game, but I couldn't load the data because the new user is not the owner... thank you EA...
I'll just have to finish the game without using any online content, and then switch to the other user to be able to play online. At least it's better than nothing.
If EA is not aware of this issue, I hope this is helpful. If they are, they should be more specific on their instructions.
It means that the code is region locked. The code is valid for users in that region or country.
Since you bought the game via Amazon, they should have a return policy.
Region locking is primarily done for legal reasons (different ratings laws, disclaimers, etc.) and to prevent people for ordering games from countries where the currency exchange is not favorable (ie. you get the game for cheap but EA doesn't make much on the sale).
