fsolve and fortran coded function

Hi, to speed up my matlab program, I coded the function of a system of nonlinear equations in fortran mex file, and then tried to solve this in fsolve. The fortran coded mex function works because I can insert x values and check the outcome of the equations. But it seems not solving by fsolve.

The fortran coded eqSystem taking the initial x0 just directly falls through fsolve without being solved at all. I checked the solution is exactly the same as my initial guess x0 and the errors of the equation system are not close enough to zero. Would you please advise what might be reasons for this to happen?

Thank you!