They are not in the mood for attention
Cats have their own unique personalities, and some cats are simply more social than others.
Cats can also ignore their humans if they are feeling stressed or anxious.
Sometimes, cats will ignore their humans because they are trying to get their attention in a different way.
If your cat is ignoring you and also shows other signs of illness, such as loss of appetite, vomiting, or diarrhea
Reward them with positive reinforcement when they do give you attention.