Territory—Some cats will not use litter used by another cat. Multiple litter boxes are an option. Never have more than two cats per litter box.
Litter Choice—Any cat may resist a new filler if it smells or feels different, so mix in a new type of filler a little bit at a time. If your cat still doesn't adapt, stick with your original filler. Because of a kitten's playful nature, you may prefer a conventional clay-type filler.
Dirty Litter Box—Cats are very fussy about cleanliness. Remove waste daily and replace conventional litter weekly. But don't clean the box with ammonia. Cats have an aversion to it. Try using warm water and a mild soap - rinse thoroughly.
Privacy—Avoid placing the litter box in a high-traffic area. Most cats, like humans, prefer privacy.
Illness—Cats can't talk, but they can give you clues. One of the most common symptoms of Feline Urinary Syndrome (FUS) is failure to use the litter box. FUS is a life-threatening illness. If symptoms persist, see your veterinarian.