You have to enter the 2020 AGI from the federal tax return Form 1040 Line 11 to e-file the 2021 tax return.
If you have entered the correct 2020 AGI and the IRS rejects the return for the 2020 AGI then the IRS probably does not have your 2020 AGI in their database.
Enter a 0 (zero) for the 2020 AGI and e-file the 2021 tax return again.
