Open the 2020 program on your computer using the 2020 program... does it open correctly ? If so then save the .taxfile again to your hard drive only and not to a back up drive.
Then start a new ONLINE return by going here and choosing a program first ... click start for free ... do NOT log in first. https://turbotax.intuit.com/personal-taxes/online/
First thing you are asked is if you used TT for 2020 and how ... that is the way to transfer the 2020 tax file.
