if your cage is glass and in an area where there is foot traffic it may never eat. young ones are very easily disturbed and when they're disturbed they won't eat.

as others have said they need to feel secure.

although i have had great success on paper towel as a substrate, if your snakes won't eat then you may want to try mulch or some sort of soil/dirt/peat mixture. refer to ross's reproductive husbandry of pythons and boas.