Update: I left TurboTax alone for a few days and then re-filed earlier this morning. When I went to fix my state return, I got a prompt to enter my IL-PIN or Driver's License/State ID. I entered my IL-PIN and re-submitted. A few hours later, I got an email saying that my state return was accepted! If you are dealing with Reject Code IL1040-8100-1, you may just have to wait a few days before refiling as it might just be a weird glitch on TurboTax's end.
