Soursop tree of five years

[Vegardner]

I'm in zone 10, my Soursop tree only produced 1 perfect fruit this year, the rest has been buds that turned brown and died off the tree. What did I do wrong?

 

[Raintree]

It's most likely a pollination issue, you can look up how to pollinate by hand.
When I was a kid soursop ice cream was one of my favorites along with tamarind ice cream.