AGI is Adjusted Gross Income
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. If you didn't file a 2018 return you enter 0 for the AGI.
How to find the AGI.
When did you file 2018? If it was late in the year try putting in zero for the AGI. And see, https://ttlc.intuit.com/community/rejections/help/what-if-i-entered-the-correct-agi-and-i-m-still-ge...
If your spouse died during 2019 there is a problem efiling and you will have to mail your return
How to correct the AGI
If you can’t get it to efile you will have to print and mail it.
How to mail a return from the Online version
Be sure to attach copies of your W2s and any 1099s that have withholding on them. You have to mail federal and state in separate envelopes because they go to different places. Get a tracking number from the post office when you mail them for proof of filing.
For AGI Reject code 031