Your 2020 tax return was more than likely rejected for the 2019 AGI. Since the 2020 tax return can no longer be e-filed the 2019 AGI is no longer necessary to file the tax return.
To access your current or prior year tax returns sign onto the TurboTax website with the User ID you used to create the account - https://myturbotax.intuit.com/
Scroll down and on the section Your tax returns & documents. Click on the Year and Click on Download/print return (PDF)
A 2020 tax return can only be printed and mailed, it cannot be e-filed.
Print, sign, date and mail the tax return to the IRS. Include with the mailed return any forms W-2 and 1099 which have taxes withheld. Go to this IRS website for mailing addresses - https://www.irs.gov/filing/where-to-file-paper-tax-returns-with-or-without-a-payment
There are no penalties for filing a tax return after the due date if filing for a tax refund or there are no taxes owed.