Unable to Electronically Submit Illinois Return Because Form IL-4644 Makes e-file Ineligible

I received a message from TurboTax stating my Illinois State return was ineligible for e-file because Form IL-4644 is part of the return. I'm hoping for your comment on the following three points: 1) I want to confirm this is the case; I can't e-file. 2) Also, wondering why this Form makes the return ineligible for e-file. Finally, 3) I don't recall being prompted last year to separately report sales from an employer stock purchase plan on the Illinois form. Thank you.