SU Pro 2018
LibFredo6_v8.1h

I didn't touch or edit any of the files, but it looks like my SketchUcation plugin may be bad, too, because I had to manually install all the Fredo6 extensions/plugins into the Plugin folder. There was no automatic install option. Should I uninstall all Fredo files and start over?

I tried to install several Fredo6 extensions, but I get this message upon opening SketchUp:

Error Loading File Fredo6_!LibFredo6.rb
Error: #<ArgumentError: invalid byte sequence in UTF-8>
c:/users/jwitzke/appdata/roaming/sketchup/sketchup 2018/sketchup/plugins/fredo6_!libfredo6/lib6core.rbe:804:in match' c:/users/jwitzke/appdata/roaming/sketchup/sketchup 2018/sketchup/plugins/fredo6_!libfredo6/lib6core.rbe:804:in block (2 levels) in load_from_config'
c:/users/jwitzke/appdata/roaming/sketchup/sketchup 2018/sketchup/plugins/fredo6_!libfredo6/lib6core.rbe:803:in each' c:/users/jwitzke/appdata/roaming/sketchup/sketchup 2018/sketchup/plugins/fredo6_!libfredo6/lib6core.rbe:803:in block in load_from_config'
c:/users/jwitzke/appdata/roaming/sketchup/sketchup 2018/sketchup/plugins/fredo6_!libfredo6/lib6core.rbe:801:in foreach' c:/users/jwitzke/appdata/roaming/sketchup/sketchup 2018/sketchup/plugins/fredo6_!libfredo6/lib6core.rbe:801:in load_from_config'
c:/users/jwitzke/appdata/roaming/sketchup/sketchup 2018/sketchup/plugins/fredo6_!libfredo6/lib6core.rbe:1215:in block in load_all_plugins' c:/users/jwitzke/appdata/roaming/sketchup/sketchup 2018/sketchup/plugins/fredo6_!libfredo6/lib6core.rbe:1215:in each'
c:/users/jwitzke/appdata/roaming/sketchup/sketchup 2018/sketchup/plugins/fredo6_!libfredo6/lib6core.rbe:1215:in load_all_plugins' c:/users/jwitzke/appdata/roaming/sketchup/sketchup 2018/sketchup/plugins/fredo6_!libfredo6/top_libfredo6.rbe:245:in startup'
C:/Users/jwitzke/AppData/Roaming/SketchUp/SketchUp 2018/SketchUp/Plugins/Fredo6_!LibFredo6.rb:63:in process' C:/Users/jwitzke/AppData/Roaming/SketchUp/SketchUp 2018/SketchUp/Plugins/Fredo6_!LibFredo6.rb:70:in module:LibFredo6_Loader'
C:/Users/jwitzke/AppData/Roaming/SketchUp/SketchUp 2018/SketchUp/Plugins/Fredo6_!LibFredo6.rb:28:in <top (required)>' Error Loading File Fredo6_Curvizard.rb Error: #<TypeError: can't convert nil into an exact number> C:/Users/jwitzke/AppData/Roaming/SketchUp/SketchUp 2018/SketchUp/Plugins/Fredo6_!LibFredo6.rb:79:in -'
C:/Users/jwitzke/AppData/Roaming/SketchUp/SketchUp 2018/SketchUp/Plugins/Fredo6_!LibFredo6.rb:79:in <top (required)>' C:/Program Files/SketchUp/SketchUp 2018/Tools/RubyStdLib/rubygems/core_ext/kernel_require.rb:54:in require'
C:/Program Files/SketchUp/SketchUp 2018/Tools/RubyStdLib/rubygems/core_ext/kernel_require.rb:54:in `require'
C:/Users/jwitzke/AppData/Roaming/SketchUp/SketchUp

Any suggestions?

Yes. Everything appears as it should!
My other plugins work perfectly, and I have had no problems.

It shows up in my plugin folder, but when I restart SU8, it doesn't show up in the extensions, or anywhere else, for that matter!