Cherries shrivel up and drop on an otherwise healthy tree
Almost all cherries (sweet0 need a pollinator cherry tree, such as a Van or Sam, or Raineer or sour cherry.
Cherries which are not pollinated grow to about pea size, turn yellow an drop off. A classical pollination symptom. If the cherry seed is empty, no pollenation. If the seed is full, then the bloom was pollenated.