Hi Marcus
I'm just a fellow simmer in the UK, but I believe that the file the system can't find is C:\X-Plane 11\Resources\shaders\legacy.glsl (not shafers).
Go into File Explorer, click on Local Disk (C:), double click on the 'X-Plane 11' folder, then the 'Resources' folder and then the 'Shaders' folder and look down the list of files.
You should find the legacy.glsl file in there. If not let me know?
Regards