I believe that the IRS won't accept your return because they haven't processed your 2019 return yet.  As a result they can't tie out to your AGI.   The IRS has indicated in a Jan update that to e-file your 2020 return you should simply change 2019 AGI indicated on TurboTax to zero.   For joint returns be sure to adjust both parties' AGI.

This solution works and TurboTax should alert other users who are having their 2020 returns rejected. 

AGI = zero works for some filers, but not always.