Here are some of possible reasons and solutions:
1. Dirty Litter Box.
Cats have 200 million odor-sensitive cells in their nose compared to our 5 million. If your cat is turning up her nose at the box and eliminating elsewhere, it could be that it’s not clean enough and offends her sensitive nose.
Clean the box often. Scoop out the soiled litter and solid wastes daily or twice a day, and change the litter and clean the box. Don’t use harsh cleaners, such as bleach, to clean the box; they may offend your cats’ delicate sense of smell further and add to the problem.
Ultimately, you and your cat will have to reach an agreement on the cleaning frequency.
Location is also vital. If your cat doesn’t like the litter box’s location, she may not use it. Cats like quiet, safe, private places to do what they have to do so find a location that allows for privacy, but is accessible and convenient for cleaning.
Locations to avoid: Do not place the litter box too close to her food and water dishes, she may avoid the box since cats don’t like to eat and eliminate in the same area. Do not place the litter box near areas that may stress her out such as the washer or dryer. If you have multiple cats, separate the litter box locations for each cat.
Follow your cat and observe what’s going on. Try several locations until you find one she will use consistently.
3. Litter Changes
If a change in litter box behavior occurs after you’ve switched the type or brand of litter, try changing back. Your cat may not like the new litter.
4. Box Issues
She may reject the box if, for some reason, she doesn’t like it. Hooded litter boxes are popular with some cats, but most don’t like the confining nature of them and feel trapped when using such a box – a particular problem in multi-cat households with dominance disputes. Older cats, or cats with health problems, such as arthritis, may have trouble stepping into boxes with high sides, or into boxes with smaller openings. If cats have any health problem that makes movement difficult, provide a sturdy ramp in front of the box, and a step down inside, if needed.
Some cats dislike litter box liners. Remove the liner if you notice your cat pulling it up or leaving claw marks in the plastic.
Providing several boxes of different sizes and types may help resolve the litter box problem.
5. Environmental Changes
Cats don’t like changes in their environment. If your cat stops using the litter box after a change has occurred, it could be that the change is causing her to become anxious. Anxiety is one of the more common feline emotional problems, and may contribute to a number of behavior problems, including house soiling.
6. Territorial Disputes
If you have more than one cat, disputes can arise over litter box usage. The solution is to provide a litter box and a private location for each cat. As a rule, you should have one litter box for every cat in the household.
If this is not possible, consider keeping an extra box in another location to circumvent disputes or clashes. If a cat doesn’t want to approach the main box area while another cat is there, she has an alternative (acceptable to you) to do her business. This prevents the cat from choosing a less acceptable location if the need is urgent.
Hope these were helpful!