As I noted in my initial post, I was hoping that I could get a copy of TT 2021 and see if the program from the same year might allow me to re-open the return directly from the PDF and then re-create the .tax2021 file. Unfortunately, it is only available for sale. As I mentioned, I wrote to several members of the Intuit executive team in hopes I might get a copy of that program so I could see if this alternative worked. I have not heard back from them.
