If you are getting a "Sucessfully registered to Zone [Could Not Determine]" following a zac reg, perhaps after imagining try this:
In ZCC > Click Configuration > Locations > Unknown > Server tab > Configuration Servers > Add at least one server.

Then try registering devices again.

I have just had a discussion with Novell Support at we discovered that during registration the "Closet Server Default Rule" is ignored for the "Unknown" location, so if you don't have any servers in the "Unknown" location the Zone info doesn't get picked up.