SSR-EP10

Hello, I have a Ingersoll Rand SSR-EP10 Air Compressor, it runs but there is no air getting to my machinery it has been running fine but came in this morning to get caught up on work and we had this problem. could it be that it needs coolant, i can not see the little window as that part of the compressor is against the wall. My Husband always took care of this stuff, but he passed away last year and i am left to figure stuff out for myself.