may stop using the litter box is they simply don’t like where it’s located. place the litter box in area where they have privacy. it should also be placed where they can get away fast if they feel “threatened” as well.
just not feeling the litter box setup.
cats may also refuse to use the litter box if they don’t like the litter box itself. it could also be due to not liking the litter that you are using. this would be something you should definitely consider. especially if you just changed to a different litter.
there is an unfortunate reason why your cat may refuse to use the litter box. your cat 