What should I put for my 2019 AGI if this is my first year filing? The IRS rejected my return when I tried to put in 0.

You were correct to enter $0 as your 2019 AGI since you didn't file in 2019.

• Just verify that the AGI is the reason you're getting rejected and not because of mismatched name and Social Security Number.
• If everything else is correct, your return may be one of the ones that can't be e-filed and must be mailed in.
• You can try and call the IRS to verify your information at 1-800-829-1040.

 

This is common. We even have a TurboTax FAQ. See What if I entered the correct AGI and I’m still getting an e-file reject?

 

Note:  How much you made and the AGI needed for filing are not the same. The AGI is the adjusted gross income after all the deductions were allowed but before the credits. Source: AmyC

 

Listen this is getting on my last nerve. I want to change to file by mail.

I want to change from efile to mail return

Please follow the instructions here to change from e-file to mail in.