Longan should be self fertile,but produce less fruit if grown individually.
Looks like you are in the proper growing climate-not humid Singapore or The Phillipines. Longan need a definite cool and dry season to set fruit. I'm sure there might be 1 or 2 trees in the Phillipines that are atypical of the species.
Perhaps air layers of named forms differ in productivity.
It's not as tropical as Lychee.
