Safari Can't Install This Extension

If you are trying to install the Button on Safari and get the following error, you can try the suggestions below in order to resolve the issue:
Try following these steps IN ORDER:
  1. If you haven't tried this yet, try restarting your Mac and doing the install.
  2. If that didn't work, check if you already have the iConsumer Button installed on your Mac.  Go into Safari and open the Preferences screen, then choose the Extensions tab.  If you find the iConsumer Button there, uninstall it. Then you should be able to re-install.
  3. If that doesn't work, go into your finder and choose Go > Go To Folder.  Put in "~/Library/Safari/Extensions".  Look for anything that says iConsumer and delete it.  Then empty the trash on your computer.  Open Safari and try to download and install the iConsumer Button again.
  4. If the three steps above don't work, this video shows a bunch of techniques which might work:
  5. This is one more suggestion from Apple: