IPlugLogger.h creates a Trace file on the root of the C drive on Windows:
char logFilePath[100];
#ifdef OS_WIN
sprintf(logFilePath, "%s/%s", "C:\\", LOGFILE); // TODO: check windows logFilePath
#else
sprintf(logFilePath, "%s/%s", getenv("HOME"), LOGFILE);
#endif
mFP = fopen(logFilePath, "w");
Unfortunately on Windows, writing to root directories requires administrator privileges. MSVC opens without them by default, so the file creation fails.
Writing to a subdirectory, eg. C:\Plug2 works without admin (ideally the code should create the directory first if needed).