The Mayo Clinic [4] describes a nursing strike as an occurrence when a baby refuses to nurse. These can happen for a few different reasons, one being the supply of milk, another may be normal growth and development, but in others, it may be a sign they are not getting enough milk from nursing.
Additionally, If a baby finds bottle feeding (either pumped breastmilk or formula) to be faster and easier than nursing they may refuse to nurse. This refusal to nurse is called a nursing strike and can be solved by continuing to offer time to nurse before offering a bottle each time.