There is a link to the IK Multimedia site (Amplitubes maker) in one of the readme files that came with 2012. If you successfully created your account - and it seems you did - you should be able to enter the serial number there (or get it from there if you need it). You can register the program 4 or 5 times w/o extra cost so you can put it on a laptop, desktop and reinstall it a few times.
This link might work:
http://www.ikmultimedia.com/index.php?Community