Dimitri,
Welcome to the Centrify Express community.
Two years ago, due to abuse, the Centrify Express program changed and deprecated some of the features that were designed for commercial customers including the one your're trying to use.
Announcement: http://blog.centrify.com/introducing-centrify-serv
FAQ: http://www.centrify.com/express/linux-unix/faq/
You can accomplish similar functionality by using any of these methods:
- SSH Allow(Users|Groups)/Deny(Users|Groups) directives
- The accesss.conf mechanism
- The PAM if_succeed.so shared object
R.P