State Tax (IL) keeps saying to change military pay (line 21 schedule M), but it is correct and pulling directly from Federal forms. How do I get it to accept?

When you get to your state return did you double-check that your military pay is entered correctly on the "Military Pay Exclusion" screen?

Also, make sure that you checked the active-duty military box for the W-2 on the "Do any of these uncommon situations apply to this W-2?" screen right after you enter your W-2.