If you didn't work last year and didn't file taxes then you would enter 0 as your AGI (Adjusted Gross Income). If you are filing jointly with a spouse, you will have to enter the correct AGI from last year if you filed together last year (you and your spouse have the same AGI ).
If you entered the correct AGI and keep on getting rejected , see here - What if I entered the correct AGI and I’m still getting an e-file reject?
If your return got rejected because your AGI (Adjusted Gross Income) does not match IRS records, you can follow the steps below to fix it (if you have already tried to efile a few times, you may have to file by mail- How do I print and mail my return in TurboTax Online?):
https://ttlc.intuit.com/replies/6079524