My CC subscription recently expired, so instead of renewing it I reinstalled my old CS6. Now, every time I try to open CS6 programs, I get the CC message saying they need to verify my subscription. Needless to say, I end up being unable to open anything. My CS6 was originally in the form of a CD, and when I reinstalled it I used a download link and the serial number on the box.
I'd try signing out of the Creative Cloud app from its Preferences > Account tab. After that when you launch your CS6 product you should be able to enter a serial number.
If you don't get the options after doing that another thing to try would be to use the Adobe Cleaner Tool - http://helpx.adobe.com/creative-suite/kb/cs5-cleaner-tool-installation-problems.html
and choose the option to remove your Adobe ID info. I think that's option 8 from within the tool.
Hope that helps,