Sit down with an attorney and all relevant documents to discuss. It may be the case that you should file suit against the insurance company. Good luck!
Robert T. Kuehl
Kuehl Law, P.C.
You should confer with an Illinois attorney, and provide him or her with your insurance policy, denial letter, and any other materials relating to your claim (claim documentation, original insurance application, EUO transcript, if any, etc.).
It's possible the insurer is taking the position that you misrepresented something on your insurance policy application, and as a consequence, they are not obligated to pay your claim.
Best of luck.
My comments above are a general response to your inquiry, and should not be considered or relied upon as legal advice. You should seek legal advice from a lawyer admitted to practice law in the relevant jurisdiction and who is familiar with the facts and circumstances of your case/issue, and the law applicable thereto.