I was the one working on this back then. I don't have the files anymore as I switched to another approach, but the process I gave back then worked.
You can try being more explicit about the arguments like this:
where a normal Fortran call would be
where argreala, arginta, argrealb and argrealc are real or integer matrices as appropiate, and argintb is an integer in Fortran. The Fortran subroutines are in the library called forlib.dll.
After defining the arguments as the appropriate types in your Maple code like
argreala:=Matrix(5,3,datatype=float): # fill in the terms in argreala after this
the call in Maple is just
This process worked for a single Fortran subroutine when I used it back then, and so hopefully it still does.