[Zope] Installing new objects

[Alexander S Coventry]

Hi.  What does it mean when a newly installed object fails to show up in
the "Available Objects" list of the Zope Contents page?  I have been
trying to install Ken Manheimer's Tracker.  I put the TrackerBase object
in the lib/python/Products, copied Tracker.zexp to the import directory,
made a symlink from Extensions/TrackerMethods.py to
lib/python/Products/TrackerBase/TrackerMethods.py, 
and restarted zope.  The TrackerBase object does not show up in the
"Available Objects" list, and attempting to import Tracker.zexp gives
the error "The object Tracker does not support this operation" along
with an uninformative-looking backtrace.  On the other hand, the
TrackerBase did turn up when I did a "Find."

Any advisce on where I should go from here?

Alex.