After you file

I am using Turbo Tax online; in "Tax Home", at the bottom of the page, is a link to open the ".tax" file for my return.    When I download the file, and then try to open it, my computer doesn't recognize the file and sends me to the Microsoft store to look for a program.   If this is a turbo tax file, why doesn't it open?    I called a support person on this and she said I had to have the CD version in order to open this file.  If that is the case, WHY do you even put it up in Turbo Tax Online for customers to download, if they can't then open the file using Turbo Tax Online?   Or, if it is only able to be opened using the CD version, why is there not an explanation below the link warning users of just that?