Hmm. The extension of the second file should be .7z. You might try changing .txt to .7z.
If that doesn't work, then please try installing the Creative Cloud app. Go to the Apps tab, set the Find New Apps section to Previous Versions, and click the Install button. That should open a list where you can select CS6. (I didn't learn until a few days ago that Creative Cloud had made it so easy to get an older version.) What I don't know is whether that avenue will work if you have a perpetual license rather than a cloud subscription.