Fortran simulation error in Simulink

I have a legacy Fortran code that I want to simulate in Simulink using S function. I compiled all the Fortran subroutines and linked it to c-mex function. However, when I attempt to simulate the s function, it gives the following error.

Moreover, upon running the simulation, some of Fortran subroutines have worked properly by reading the variables stored in text file and subsequently writting the initialized variables into the new file.

I can't figure out where exactly the problem lies: in Fortran code or C mex function.

What does the above error imply?

Thankyou.