The 2017 AGI to file your 2018 return?  You don't need it anymore.  That is only needed to efile.  You now have to print and mail prior year returns.

If you are filing a 2019 tax return you need the 2018 AGI to electronically file the 2019 tax return.  The IRS uses the 2018 AGI as your electronic signature and for taxpayer identification.

The 2018 AGI is on the 2018 Federal tax return you filed Form 1040 Line 7

https://ttlc.intuit.com/community/agi/help/how-do-i-find-last-year-s-agi/01/25947

To access your current or prior year 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)

Or go to this IRS website for free federal tax return transcripts - https://www.irs.gov/individuals/get-transcript

If your tax return continues to be rejected with the 2018 AGI then enter a 0 (zero) for the AGI and e-file again.

If this is also rejected then you will have to print and mail the tax return.

See this TurboTax support FAQ for printing a tax return for mailing - https://ttlc.intuit.com/community/printing/help/how-do-i-print-and-mail-my-return-in-turbotax-online...

A 2017 AGI is not needed to file a 2018 tax return since the 2018 tax return can only be printed and mailed.

The TurboTax online editions are only for tax year 2019.

To complete and file a 2018 tax return using TurboTax you would need to purchase, download and install on a personal computer one of the 2018 desktop editions from this website - https://turbotax.intuit.com/personal-taxes/past-years-products/

A 2018 tax return can only be printed and mailed, it cannot be e-filed.

I do need it because it wasn't filed properly in 2017 and now I owe taxes plus fees because it was input incorrectly. Now I need it so I can pay those fees.

A 2017 return cannot be e-filed, so you do not need to enter an AGI.  AGI is only needed for e-filing.  Your 2017 return must be filed by printing, signing and mailing it in an envelope.

You need to go to the account in which you prepared the return.  If you have any changes you need to make you must download 2017 software to make the changes.  Adding AGI is not necessary at all.

https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-finish-a-prior-year-return-that-i-...

. If you have any changes/corrections at all to make to your 2017 return, you now have to complete it using desktop software, which you must download to a full PC or Mac  (not to a mobile device).Then you need to print, sign and mail it.

https://ttlc.intuit.com/questions/2559403-how-do-i-finish-a-prior-year-return-that-i-started-in-turb...

If you already paid for your online software you can ask customer support for a download of the desktop software.

They are available from 5 a.m. to 5 p.m. Pacific time Mon-Fri.

If you are getting a refund, there is not a penalty for filing past the deadline.  If you owe taxes, the interest/penalties will be calculated by the IRS based on how much you owe and when they receive your return and payment. The IRS will bill you for this; it will not be calculated by TurboTax.

Do you know how to find your account?

Many people have multiple TT accounts and forget how to access them.  Log out of the account you are in now.

Account recovery

https://myturbotax.intuit.com/account-recovery/

https://ttlc.intuit.com/questions/1901535-forgot-your-turbotax-online-user-id-or-password

Or did you use the desktop version of TurboTax?  If so, the files are on your own hard drive or any backup device you used like a flash drive.

https://ttlc.intuit.com/questions/1901486-how-many-turbotax-accounts-do-i-have

https://ttlc.intuit.com/questions/1901535

https://ttlc.intuit.com/questions/1901659-find-your-tax-data-file-in-mac

https://ttlc.intuit.com/questions/1900721-find-your-tax-data-file-tax-file-in-windows

To get a copy of your previously filed returns prepared with online TurboTax https://ttlc.intuit.com/questions/1900748-how-do-i-get-a-copy-of-a-return-i-filed-in-turbotax-online

https://ttlc.intuit.com/questions/1900748-how-do-i-get-a-copy-of-a-return-i-filed-this-year-in-turbo...