If the IRS is rejecting your 2018 tax return for the 2017 AGI, make sure you are entering the correct AGI.
To access your current or prior year online tax returns sign onto the TurboTax website with the userID 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 View adjusted gross income (AGI)
You can also get free transcripts of your federal return from the IRS - http://www.irs.gov/Individuals/Get-Transcript
If the IRS continues to reject the tax return for the AGI, then try entering a 0 (zero) for the 2017 AGI. If this is also rejected then your only other option is to print and mail the tax return.
See this TurboTax support FAQ for the procedure to print a tax return for mailing when using the online editions - https://ttlc.intuit.com/community/printing/help/how-do-i-print-and-mail-my-return-in-turbotax-online/01/26258