Missing local files permission
Gesturefy doesn't work for local files without the access local files permission.
1. Go to the Firefox add-ons page (about:addons or Ctrl + Shift + A)
2. Navigate to extensions and click the Gesturefy entry to expand it.
3. Switch to the "Permissions and data" section and grant the "Access local files on your computer" permission.
You may have to reload affected pages afterwards.