Disability formal request per ERISA 1974 as amended.

I recently received a letter from my benefits group saying disability would no longer be paid and advised to submit formal request as specified by the Employee Retirement Income Security Act (ERISA) 1974 as amended. What is the formal request process? I am not able to return to work and my Doctor is informing the insurance company my condition is worsenig. Please advise me on the correct manner to proceed, so that I am not delayed by the insurance company asking for additional infromation or a proper submittal. What other options do I have if long term insurance benefits have run there course and I am not able to return to any profession at present. Additionally, if disability has indeed run its course, can I apply or approach the company about workman's compensation? I was became affected while on the clock with my current medical condition.