If the leo won't eat on its own, I would first take it to a vet and get it check out for internal parasites.

Second, if it still won't eat...what I have done in the past with rescue leos was to make a slurry of crickets, mealworms, superworms with pedialyte and literally syringe feed the leos. After a few feedings I found that they would take right to the syringe without issue.