Having the same issue.. see post by me below about worm factory and idea. Hint don't do what I did.

chippate, we need more info. I would guess your system is usually called a "flow-thru" system. Does it have a grate of somesort on the bottom? How big is it,how old is it, what do you feed,how many worms???? I do not have a flow-thru but have read that sometimes the worms escape down. A very small light in the harvest area may solve your problem.

More info should get you more responses.