There are various common reasons for denying a claim. They include that you were not injured at work, your injury is pre-existing, or you didn’t notify the employer that you were injured in a timely manner.
An additional reason for denial is the assertion that your misfortune does not meet the definition of a genuine accident. For example, suppose you’re doing typical work at your job. Nothing different happens from the norm, yet you suddenly experience pain. In that case, it may be very difficult to prove the injury was work-related.