If Centrify is loaded in your system and has been joined to AD, all your AD users (form the current domain or any trusted domains should be visible).
Please we are assuming " bruce" is a valid AD user (substitute bruce with a valid AD user otherwise)
Show me the output of:
$ adquery user bruce
If the output of this command is " bruce is not a zone user"; this means that this user is not a valid AD user.
$ cat /etc/nsswitch.conf | grep centrifydc
This is to verify that the name service switch entries are in place.