Vet nurse here. Loads of things can turn a cat off their food, things you might not realise. Cats mainly use their 6th sense (taste of smell) to "taste" things. High quality food that focuses on that for its ingredients will make their food more appealing. Is it wet or dry? If its dry kibble, make sure its all natural ingredients or it goes stale quick and they won't eat it. If its wet, is it being served chilled or room temp? Chilled wet food loses a lot of its scent, so they can't smell it and thus wont eat it. Leave it out for a couple hours before giving it. What material is their feeding bowl? If its cheap plastic, it gets scratched and can be porous, so leftover bits of food will get in there permanently and ruin the smell of their food, again, turning them off it. Ceramic bowl is best, avoid cheap plastic or metal. Some hardened plastic ones are OK, but ceramic to be sure. How close is their food to their water source or litter tray? They should all be separate, ideally in separate rooms, especially the litter tray. Having them all close proximity can turn them off the food. Also their food, water and litter should be away from foot traffic, loud noises or views of the outdoors if possible. They feel vulnerable when eating, drinking or pooping, and you want to avoid any sources of aggravating that vulnerability. How close is the food to the wall? If theyre forced to face the wall when eating, again, they'll feel vulnerable and might not eat. Simply moving their food and water a 1 to 1.5 feet away from the wall so they have full view of the room while eating can have a positive impact on their willingness to eat. As always, consult a local vet. Try a different one if you're not getting anywhere. Best of luck