I haven’t filed my Illinois state return for the last two years because I didn’t have the proof that I was an Illinois resident. I do now, what do I do?

Not sure what proof you thought you needed in order to file your IL tax returns.   IL is pretty picky when it comes to e-filing and will not allow you to e-file an IL return without an IL driver's license or state ID, but that did not prevent you from preparing and filing those returns by mail.

If you are getting a refund for the state return there will not be a penalty for filing late; if you owe tax to IL you will now owe with penalties and interest, for which the state will bill you.

You are too late to e-file a past year IL return; a 2023 IL return can still be e-filed if you successfully e-filed a 2023 federal return.   If you used TT to prepare your past year federal return you can use the CD/download software to prepare the past year IL return---it will require using a full PC or Mac, not a mobile device.  Or you can get the forms from the state website and prepare them by hand to mail in.

https://ttlc.intuit.com/questions/2559403-how-do-i-finish-a-prior-year-return-that-i-started-in-turbotax-online

https://ttlc.intuit.com/community/state-taxes/help/how-do-i-contact-my-state-department-of-revenue/00/25573