So, we have a kitten, about 6 months old. She will urinate in the litterbox, but that's it. We actually have 2 boxes, both clean (as far as litterboxes go).

It's getting old cleaning up after her and she may have to become an outdoor cat if we can't get her to use the box soon.

She had some health issues which the vet treated her for, so she is ok now but during that time, she had the running poops! As soon as she would start pooping, she'd start running! At least she stopped running!

Also, when she urinates in the box, she does not cover it up (she's not our only cat) like most cats do.

We have 3 other cats that are regularly in the house and they all use the litterbox as expected.

 

I would get a different brand of litter and another litter box. Shut the kitten up in a small room (bathroom) with her own litter box and see if she learns how to use it.

If she doesn't like the current brand of litter the new brand might work. And, if there is a behavioral thing going on with the other cats, shutting her in a room by herself might remove that influence.

 

Our two cats very nicely share one litterbox. I do notice that if one is in the box (in basement) and they think they hear us at the stairs, they will run out of the box quickly. There does seem to be this desire for privacy/quiet/security/who knows? It may be instinctual to feel vulnerable when they are in the box. Maybe it’s afraid of the other cats, at least at that moment. Try it in a quiet, out of the way location if it isn’t already.

 

Pilot Dane has the right idea and suggested exactly what I would suggest. Another thing that happens is after an illness, such as your kitty had, they can forget that the box is where they needs to go. You also may want to add one more box as often cats prefer to have their "Own" box.