**UPDATE*** for anyone else (I can't imagine I'm the only one) who has this problem.
I was able to resolve this -- sort of. What I mean is I was able to prepare my 2020 tax return and get 2019 data in there. What I did was retuned the Costco version of turbo tax (yes, even though it's online and should work, and even though I already registered the registration code online....) and what this did was delete the work I had already done on the 2020 return. (I could not delete it myself and start over, which I wanted to try to see if I could upload the 2019.tax file to the system, which was not working for some reason with my 2020 data in there).
Once the 2020 return data was gone (after my return to costco, they deactivate the code) I was able to go to "tools" then "upload previous year tax return" (do not just upload the PDF), it has to be the .tax file.....
Once I did that I was able to see my 2019 data and do side by side comparisons, all my data was imported and it worked smoothly.
What I don't know is whether there's a way to get here WITHOUT giving up the Costco discount.... so maybe I didn't need to really return the costco product if I uploaded the previous year's return BEFORE starting? I have no idea. But the Turbo Tax help folks had never heard of this problem before and were insisting that you cannot buy the *online* version of their software in retail stores. I shared my Costco screen print of my order to prove otherwise....
Good luck!
