I filed my 2020 taxes with TurboTax but for this year it does not recognize it in order to verify AGI, which caused my refund to be rejected. What should I do next?

If the IRS has not processed your 2020 return yet, they may not yet have recorded the AGI. I read last year that if that happens, entering an AGI of $0 (for E-file purposes only) will allow the E-File to go through. I don't know first hand if that is true or not, but it shouldn't hurt to try. If not, you'll have to mail in your return.

@T_Wheeler is correct. 

You may need to enter “0”. Please see this Help Article for more information and to see if any of these situations apply to you. 

@amleonard12