There could be several reasons why your
cat will not eat. Take a look inside your cat's mouth and under its tongue if you can do it safely. If you see any redness, inflammation or bleeding of the gums or around teeth, there may be
periodontal disease present. Confirm there are no foreign objects (or string) in the mouth or under the tongue. If you see anything that does not appear "normal", schedule an exam with your veterinarian. Other potential causes include
kidney disease,
pancreatitis or gastrointestinal issues. These may require blood work and x-rays to diagnose.
If the mouth is clear, try warming the food slightly or adding some liquid from a can of tuna to stimulate appetite. If your cat does not eat for 3+ days, see your vet immediately to avoid complications involving
liver function.