..! New kitten.

Akiong has a good point. You really need to watch the kitten to see if she is going to the bathroom. You can stimulate the kitten's bowel movements by taking a warm wet washcloth and wiping the kittens butt. This will help the kitten use the litter box, hopefully. Is the kitten's stomach getting bloated at all, she could have some sort of blockage in the stomach or bowels. It's really easy for a kitten (or any cat) to get dehydrated, which will make them sluggish. You can go a quick test by lightly pulling the skin up between the shoulder blades. If it sinks right back down, the kitten is doing good. If it is slow to go back down, the kitten is dehydrated and you need to get some fluids in pretty quick. This might take a trip to the vet to administer some fluids in by a shot.