What is the issue with the AGI?

AGI mismatch is a common problem for many e-Filers. The reason is a mystery.

If you don't have at hand the self-select PIN you invented last year, you'll have to file on paper via US Mail.

The funny thing is, the PIN is hiding in your turbotax return if you e-Filed and imported your return from last year.

Cannot see what you see, of course, but the 2017 AGI is used during e-file to protect against someone else mistakenly or fraudulently filing a return in your name and social security number.  You may retrieve that figure through the IRS website https://www.irs.gov/individuals/get-transcript

Did your AGI reject?  When did you file 2017? If it was late in the year try putting in zero for the AGI. And see this, https://ttlc.intuit.com/replies/5595742 If you can’t get it to efile you will have to print and mail it.