Are you on a Mac or PC?
In either case is SketchUp completely closed when you run the installer?
Have you restarted your machine, and gone right to installer without opening SketchUp?
If that doesn’t work, try this:
Open up SketchUp, go to “Window>Extension Manager”
In there you’ll find a list of all installed extensions. Find Fabber. Click on it, click “Manage” and uninstall it.
Then, make sure that you have a fresh download, IE get it AGAIN from our site here. Make certain you’re opening that new, fresh copy. Run the installer (if you’re on Windows)
Let the installer fully complete. Then open SketchUp and try once more. If none of that works, PM me and I can setup a screen share with you.