Check the email address for your account and make sure it is active.
Try contacting Adobe Support by phone or chat and see if they can assist you.
Phone support | Orders, returns exchanges
For the link below click the Still Need Help? option in the blue area at the bottom and choose the chat option...
Creative Cloud support (all Creative Cloud customer service issues)
http://helpx.adobe.com/x-productkb/global/service-ccm.html ( http://adobe.ly/19llvMN )
A Cloud subscription does not uses serial numbers... what did YOU buy?