I live in Jamaica were it mainly hot and cold at night I have a Muscovy female duck and it won't lay I have it almost 3year from September 2015 now its going on to September 2017 and I have access to a lot of man duck and it still won't lay
You have man ducks, we call them also drakes. There need to be three, six, or more girl ducks for each drake. She could be getting hurt, could even get killed by too many drakes mating her. She does not need drakes to lay eggs.
Muscovies are seasonal layers, they do not lay all year. Get her away from the drakes, first. Give her good quality food with enough protein and calcium and vitamins. You can orovide these things inexpensively. Crushed shells, insects, and fresh vegetables will help her.