Reply to Activation code

Hey guys, i recently bough traktor s4 from guitar center their used web site. But when i installed cd and i tried to install it, seemed to me activation code was probably used buy previous person. What should i do? Do I need to buy full version of traktr or i can get a new activation code? Any suggestions? i really do not want to return it an do not really want to pay extra 90 for a new cd. Thanks guys.