How do I respond to this error - Illinois 1040 line 1a "you must enter an amount or a zero"?

TurboTax Easy Step says I must enter an amount or a zero for Form IL-1040 Line 1a.

When I look at the Form, there is no Line 1a, only a line 1 and it has my gross income in it. In other words, I can't find a Line 1a, nor a blank line 1 on Form Il-1040. 

What should I do?