First of all you do not click on anything that says "amend" if the return was rejected. Rejected means it was not filed. You only use "amend" for a return that was accepted and fully processed in order to add information or correct a mistake. "Amend" would not be appropriate for a rejected return.
Instead, if you have any sort of corrections to make to the 2019 return, you will need to download the 2019 desktop software and make the corrections, since you can no longer use online for a 2019 return. Or you can print, sign and mail it as is--depending on why it was rejected in the first place.
Many rejections are for incorrect AGI. Since you only need AGI for e-filing, and you cannot e-file it now, the AGI does not matter.
A 2019 return cannot be e-filed. The only way to file it is by mail.
When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.
Federal and state returns must be in separate envelopes and they are mailed to different addresses. Read the mailing instructions that print with your tax return carefully so you mail them to the right addresses.
Why did it reject? If it rejected it was never filed so you do not amend. You just fix it and print and mail it now.
If you need to fix something you will need to switch to the Desktop program. You need to use a full Windows or Mac computer. And mail the return. If you paid for the Online version ask support to give you the Desktop program download.
How to finish a prior year online return
After you get the program installed the first thing to do before you open your tax return .tax file is to update the program and install any state programs you had. Then open your file. So you first might need to start a fake return to be able to download the state program (go to FILE - NEW).
Most rejected tax returns are for the prior year AGI. So if your 2019 tax return was rejected for the 2018 AGI, there is nothing for you to correct on the 2019 tax return since it can now only be printed and mailed. The prior year AGI is only used when e-filing the return.
To access your prior year online tax returns sign onto the TurboTax website with the User ID you used to create the account - https://myturbotax.intuit.com/
Scroll down to the bottom of the screen and on the section Your tax returns & documents click on Show. Click on the Year and Click on Download/print return (PDF)
A 2019 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.