Error: *.dll | OK: *.dylib

[mipsk]

Dear OpenSees community,

I have been working on an element using the dynamic API, building it in MacOS without errors.
Today, trying to check some things in Windows, some errors are given in Visual Studio. No DLL is generated.

The error is created by ---theDomain=OPS_GetDomain()--- placed inside:
OPS_Export void *
OPS_ELEMENT()
{
(...)
Domain *theDomain = 0;
theDomain = OPS_GetDomain();
(...)
}

From elementAPI.h:
extern Domain *OPS_GetDomain(void); //**MRL

The error warning in VS is:
error LNK2019: unresolved external symbol "class Domain * __cdecl OPS_GetDomain(void)" (?OPS_GetDomain@@YAPAVDomain@@XZ)

Thanks in advance!