DEAD SPACE 3 LIMITED EDITION PS3 CODE NOT WORKING

Hello! I have bought Dead Space 3 Limited Edition PS3 game. When I try to enter the code for Limited Edition Unlocks all I get is a message that my key is not valid or it has been used already, I have never used the key since I got the game from the store. Can somebody help me with this issue. I can play co-op but I can't get the extra content like the Witness Suit, First Contact Suit, Evangelizer Weapon, Negotiator Weapon.