CS6 is no longer being developed or supported. so I am not sure who can help here. There are some additional solutions here that can probably help
It's a new problem, now that Flash Pro CS6 is part of the Animate CC menu in the CC Apps tab, there's no way to update from 12.0 to 12.0.2.
The DMG on that site does update to 12.0.2, which solves the problem about getting Toolkit for CreateJS, as it was built in by then.
After installing Flash Pro CS 6 on a PC running Windows 10, I was able to install CreatJS 1.1 and without any issues. Apparently, Flash Pro (+CreatJS) can only convert very simple flash files to HTML5. At the end, CreatJS toolkit did not help me, since my flash file was complex. I ended up creating a JS slider from scratch and that took less time then figuring on how to install CreatJS toolkit.
I found out later that CS6 does get its own update notification in the CC menu, and that brings it up to 12.0.2, with CreateJS installed.
We are using Flash cs6 with latest updates. While installing CreateJS 1.2 extension we are getting this error. The extension Adobe_Flash_Professional_Toolkit_For_CreateJS does not contain valid signature. The extension will not be installed.
We are using windows operating system. For this problem any solution available.