Thank you @DoninGA for suggesting this solution to a rejected efile return due to incorrect 2020 AGI.
This solution of entering a 0 (zero) for the 2020 AGI worked for me and my 2021 federal and state returns were then successfully efiled.
Note: I had initially followed the TurboTax advice of getting an IRS transcript of the 2020 return. The IRS 2020 transcript verified that the correct 2020 AGI was being entered when I efiled my 2021 return. However, my subsequent 2021 efile was still not successful. Since I efiled the 2020 return in March 2020, one would think that the IRS' efile database would be updated by March 2021 when I did the 2021 return efile. In my case (and possibly others), it appears that the IRS' 2020 transcript database is not synchronized with the IRS' efile database.
It seems strange that entering a zero (0) resolved this 2020 AGI problem. Thanks again for suggesting this solution.
