@ahudson the following link is the hardware files. Please download this file -> DOWNLOAD <- and set your directory path as the folder labeled Step_2_Addons.

To change your directory you have to locate it using the preference tab.

File > Preferences > Sketchbook location: C:\Users\username\Documents\Arduino.
The above should be changed to Step_2_Addons.

For reference please use Lesson 1C.

https://basecamp.robolink.com/cwists/preview/171x

If this does not work, please try deleting files located in: C:$Username\AppData\Local\Arduino15\staging

Then try checking if it works again.