After 07 Feb update Still not working for the PMDG 747-400 model. Fuel truck sits underneath the main body gear and GSX does not recognize the opening doors..... 
As explained in the manual, and in all threads about both the PMDG 747 and the airplane customization in general, if you have already customized the airplane, either by doing it yourself, or by downloading a file made by another user, your own customization will always take precedence over the internal GSX data.
So, you should use the Reset button in the airplane configuration editor to undo all your changes, and restore the default config that comes with GSX. And, if you placed a GSX.CFG in the Airplane folder, instead of the %APPDATA% folder, you must remove it manually, since the Reset won't remove a file placed in the Airplane folder, since it's supposed to be the place used by airplane developers supplying their products with a pre-made GSX.CFG file, so it won't be reset until you remove it manually.
The airplane configuration page will tell you from which source GSX is taking its data from.