The screenshot shows you are using your own customization file, which is entirely unnecessary, since the PMDG 747 is internally supported. But, since user customizations always takes precedence, whatever error you made, will always be there, regardless how many times you install or update GSX, since no installer will ever touch your own customization files.
So, the first thing to do, is to remove your customization file, by pressing the "Reset" button, then Restart Couatl, so GSX will use its own internal configuration data, which surely works.