You should be able to e-file if you use your IL-PIN or IL driver's license, which are alternative methods to your prior year's AGI. If you amended or changed the prior year's AGI that's what you use. if you filed after 10/15 try zero. Try dropping pennies from the prior year's agi.
il pin
https://mytax.illinois.gov/_/#1
Maybe others can suggest other approaches, but if not and the issue can't be resolved you'll have to file by mail.
