Where is the Subscription Key? PLEASE HELP!

I have just re-purchased Norton Internet Security for Mac. After the installation , the software is asking for a "Subscription Key". I have checked my electronic invoice from the purchase and there's nothing there. I even tried using my confirmation oder number and nothing. I went in a log in  to see if the "Subscription Key" was somewhere in the record when I purchased the software an nothing.  Please HELP!!!