If SimCity isn't there, then you're either logging into the wrong account or the game isn't activated yet. 'invalid' means the code format is wrong. Should be 5 sets of 4 alphanumeric codes seperated by spaces, try without spacing. Can also happen if you're trying to redeem a box set game code on a digital code entry system (Origin site) 'used' means the code is already registered to an Origin account (digital download) Usually games that are bought via Origin will be redeemed on your account automatically after purchase.
Although you will receive a mail with the product code, this code is most likely already tied to your account. So, if you are told that the code has already been used, please check your My Games tab first and if the game is not shown there, then please contact a Game Advisor at for further assistance. Instructions on how to contact a game advisor via live chat from your computer.