Cherimoya Tree Not Producing Fruit

I believe you have to hand-pollinate the flowers. I was once based on a ranch in California where they were experimenting with Cherimoya as a crop. The first couple of years there were several people who used small paint brushes to pull pollen off of the flowers and put on the stamen. I'm not sure if you do it on the same flower, or have to put the pollen on another flower. Good luck. Cherimoya are wonderful when the pulp is blended with orange juice. A little overwhelming when eaten alone.