Troubleshooting Help Viewer
From Mac Guides
There are a variety of possible symptoms that indicate that Help Viewer is not working correctly. These include help pages not displaying, the Help Viewer application unexpectedly quitting or Help Viewer links not working, among others.
There can be many causes of these problems, but by far the most common is corrupt preferences or caches.
The problems can usually be fixed by quitting Help Viewer (if open), then deleting the following files and folders:
Note: "~" represents your home folder, ie /Users/[your username].
If deleting these items does not fix your problems, read the links below for additional advice.