Since HueForge is not an installer, you must have directory permissions to write into the Filament directory. C:\Program Files and C:\Program Files (x86) are protected directories and Windows will not allow writing into them. Documents or simply C:\HueForge or C:\Programs\HueForge will work.
My Export STL Option is Grayed Out
You have loaded and STL file as your input (most often the TD_Step_Test.stl). As such, there is no STL output to export, you already have it. HueForge does not modify pre-existing STL files.
Choosing a selection results in a full page refresh.