Just press ~ and start typing your cheats... you don't see any console or so popping up so it's 'blind'. You know you're using the console when your character doesn't move when pressing 'A' or so.
Check if you have entered the correct line in the correct place in the correct file, and you're pusing the correct key on the keyboard. (you're looking for the key above the TAB)
Besides that, I wouldn't have a clue.
(yeah, that was too many instances of 'correct' in one sentence. Live with it )