Yes if you file a return there is an AGI Adjusted Gross Income. But if you filed 2018 late the IRS might not have the AGI in the database to verify you. So you should try using 0 for the AGI to efile 2019.
You need your 2018 AGI to efile 2019. The AGI is on 2018 1040 line 7. If you filed a Joint return you use the same AGI for each spouse.
How to find the AGI.
https://ttlc.intuit.com/community/agi/help/how-do-i-find-last-year-s-agi/01/25947
