This should maybe be answered by a Turbo Tax employee; however, in the interest of getting you a quick response, I think the correct answer is that, if you are new to using Turbo Tax in 2021, then the reason you can't use Turbo Tax to download your 2019 Return is that Turbo Tax simply does not have it because you didn't use Turbo Tax for your 2019 Return. Next year, and for years after that, if you continue as a Turbo Tax customer, you will be able to access prior years' returns. Hope this helps.
PS The initial downloading of prior year's returns serves mostly to help you not have to retype basic information that Turbo Tax already has. It's not a game stopper, so you can still proceed with your 2020 Return. You'll just have to type in more information instead of having it pop up "automatically."
