Be sure you complete the NY return first, before the IL return, so that the other state credit is calculated and applied correctly.
I'd suggest you carefully review Illinois' printed instructions for Schedule CR, particularly the specific instructions on pages 1-2 for Column A and Column B. Here's a link to those instructions:
https://www2.illinois.gov/rev/forms/incometax/Documents/currentyear/individual/IL-1040-Schedule-CR-I...
If you determine that your Schedule CR is correct, and you still can't e-file it, just print the Illinois return and mail it in.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
