Feed it snails before giving it the main course. If it still doesn't touch the snail, then just leave it in there overnight. It will eventually be eaten eventually. If it doesn't eat it, then maybe the teeth is already overgrown or its already a picky eater. You can obviously tell if the teeth is already overgrown if you take a good look at the mouth.
Get "wild" shelled seafood from grocery store, no farmed raised stuff or anything with chemicals (i.e. preservatives). If its living at the time of purchase, freeze it for 1-2 weeks before feeding.