The problem is a bit obscure, but it is caused by the fact that you have HTML documentation with the same name as your main function. FEX assumes that the HTML documentation has the same name as its generating script/function, and does not show that script/function.
Change the name of your HTML documentation so that it does NOT match your main function name, and your main function will then be listed and shown by FEX.
I learned this by trial-and-error, it does not seem to be documented anywhere. I always name my HTML scripts something like
nameoffunction_doc.m
% ^^^^ add something like this!
and then the nameoffunction file will be displayed correctly... and the HTML too!
