There may be several different reasons, such as amending a return, etc.
To find your 2017 AGI that the IRS will recognize, use the IRS webpage linked below to obtain a transcript (abbreviated version) of your 2017 return. That transcript will contain your 2017 AGI so you can complete your e-filing.
https://www.irs.gov/individuals/get-transcript
*** I am NOT a tax expert. I am a seasoned TurboTax user, and volunteer to provide assistance to TT users. Nothing I post is to be considered TAX ADVICE; I bear no legal liability for responses.***
