I;ve had plenty of experience with these, they can be tricky. If you get one that feeds then your laughing as they are greedy so and sos but if you get one that doesn;t eat its difficult to get them eating.
try some live or frozen bloodworm at lights out, you can tell whenthey eat as there head stabs the worm and jerks whilst it swallows the worm
Once eating move to more substantial food