Q.Why Is Our Hedge Apple Tree Not Bearing Hedge Balls?
It has not produced any hedge balls for 2-3 years
Certified GKH Gardening Expert
It's likely a pollination problem or you have lost your pollinator tree, i.e., the male. The Osage orange tree produces female and male flowers on separate trees, so if you lost a tree or two and no longer have both male and female trees, you likely won't see the hedge apples anymore (unless there are some nearby in a neighbor's yard). Also, weather extremes such as drought can play a part.
If you still have male and female trees, try amping up your pollinator plants. Here is information below:
https://www.gardeningknowhow.com/ornamental/trees/osage-orange/growing-osage-orange-trees.htm
https://lancaster.unl.edu/osage-orange-tree
https://www.gardeningknowhow.com/garden-how-to/beneficial/insect-pollination-process.htm
https://www.gardeningknowhow.com/garden-how-to/beneficial/creating-a-pollinator-garden.htm