Origin asks to enter product key again

I need help so bad. I have bought the Titanfall at EB games for PC and installed them, and yes i put the prodcut key in. I had to reinstall because it stopped when i was downloading the game. And now i reinstalled it, and after i am about to play the game, the window "ACTIVATION REQUIRED", so i tried putting my key once again and now it says the key was already used. so now i cant even play titanfall. and i dont have it on my games tab on origin. can someone help me with this please? i paid $67 dollars and this shouldnt be happening. Im really disappointed ryt now.