Hmm so you haven't hacked at all? Your just trying to enter your code...
Well if you aren't VAC banned at all I would contact steam.
I bought GTA and the key wouldn't enter in on steam so I contacted them and it got taken care of.
EDIT:
also wrong section this is for releases only (i believe) put these questions in help section.
@PP_CrazyApple Yes, probably that. codes just DON'T WORK. espically mw2 ones.