Very strange. Mangoes set many flowers that have both male and some that are male and female parts and thus are capable of setting fruit. These blooms are pollinated by various insects. I am not sure what is going wrong with your mango trees. I suggest you contact your local County Extension Office to see what they say about it. They have local experience with such fruits and may be aware of a local problem going on with mangoes. Their contact information is:
Lee County Extension
3406 Palm Beach Blvd
Ft. Myers, FL 33916-3736
Phone (239) 533-4327
The following web site may be helpful also:
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