I made a modification to the start of the CallPlugIn function
//PyObject* pluginModule = PyImport_Import(name); PyObject* pluginModule = PyImport_ImportModule(PLUGIN_NAME);
It got me further into the function, but the result string is null.
const char* resultStr = PyBytes_AsString(resultObj);
I tried this code and it got the right result.
char *cstrret; PyArg_Parse(resultObj, "s", &cstrret);
I used this tutorial:
Its the only one I've found that works.