ep500's are amazingly well built. Tilt it back so you can look inside and press the down arrow. You should see the press rod descend. You will also hear the pneumatics activate when it does so. If it comes down, use a mirror to inspect the plunger for build up of ceramic on the alox press rod. You can also turn it off with the press rod in the down position, let it cool down and check it by feel. If you see a lot of ceramic build-up all over the top of the muffle around the press rod, you may need to remove the rod and clean it with glass beads.
Very little in these units is beyond repair, IMHO. You can likely make it work, especially if you have a second "dud" unit to cannibalize for parts.
I'll check back later.