The plug-in uses hardcoded values for locating the locale data on the installation system, which only works properly on Unix'ish systems.
When run in a Windows environment, there is a big chance of the hardcoded value pointing to the wrong or even a missing directory.
To fix this, any hardcoded path should be replaced with a call to of one of the gimpenv functions.
In case of the LOCALEDIR, instead calling "gimp_locale_directory ()" is sufficient.
If other data directories are also used by the plug-in (e.g. for registering the help file), these may need to be constructed, e.g. through:
gchar *path, *uri;
path = g_build_filename (gimp_data_directory (), "help", PLUGIN_NAME, NULL);
uri = g_filename_to_uri (path, NULL, NULL);
gimp_plugin_help_register (plugin_name, uri);