login in CMC with Administrator and go to Authentication TAB.
Add a valid AD group.
now go to the users and group section and search for any AD user.
Now try logging with any AD user now.
logging attempt can be easily seen in the tomcat logs but make sure these parameters are present:-
-Djcsi.kerberos.debug=true
-Dsun.kerberos.debug=true
Best tool to help you to identify your issue will be this note.
1560672 - How to kinit. AD user fails to manually login to Tomcat hosted InfoView.
-Raunak