Dummy argument associated actual procedure differs from dummy argument of the dummy procedure

I'm using a the function NEQNF from the IMSL Fortran Library to solve a non-linear equation system and get 3 errors. I'm using Visual Studio 2017 on a x64 system. The error says the following:

Error #7061: The characterístic of dummy argument 1 of the associated actual procedure differ from the characteristics of dummy argument 1 of the dummy procedure [FCN_SS]


Error #7062: The characterístic of dummy argument 2 of the associated actual procedure differ from the characteristics of dummy argument 2 of the dummy procedure [FCN_SS]

Error #7063: The characterístic of dummy argument 3 of the associated actual procedure differ from the characteristics of dummy argument 3 of the dummy procedure [FCN_SS]

The code is:

    include 'link_fnl_shared.h' 

    use neqnf_int
    use umach_int

    implicit none

!Declaring variables
    .
    .
    .

    Contains

    subroutine solve_ss(x, fnorm)

        integer n
        parameter (n=2)

        integer k, nout
        real(dp) :: fnorm, x(n), xguess(n)

        data xguess/1.0_dp, 0.3_dp/   !guess for total output in units

        call umach (2, nout)
        call neqnf (fcn_ss, x, xguess=xguess, fnorm=fnorm)

    end subroutine solve_ss


    subroutine fcn_ss(x, f, n)

        implicit none

        !specification
        integer n
        real(dp) :: x(n), f(n)

    .
    .
    .

    F(1)=...

    F(2)=...

    end subroutine fcn_ss

I'm not sure what the error is about, since the declaration of the variables is the same in solve_ss and fcn_ss.