There are several reasons the Workers’ Compensation insurance company will not pay for a work injury.
If your employer tells them there was no accident reported they will often refuse to pay.
If your medical records do not provide a history of being injured on the job they will refuse to pay.
If your employer claims to have witnesses who know you were not hurt on the job, or that you told someone you were injured outside of work they will refuse to pay.
If you were injured in the parking lot there are some cases in Illinois that provide, depending on the circumstances, you may not be entitled to compensation.
If the Workers’ Compensation insurance company refuses to pay you should contact an attorney and request a hearing. This will force the insurance company to hire an attorney and decide whether to defend the case at hearing, or pay you.