Which Line on your original, E-Filed 1040 are you using...must be from line 8b.
https://ttlc.intuit.com/community/agi/help/how-do-i-find-last-year-s-agi/01/25947
________________________
AGI is OK???
Then try a zero for 2019 AGI. Late/paper filed 2019 tax returns may not have a 2019 AGI in the IRS computers.
IF that doesn't work, then you are stuck with printing and mail-filing.
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*