Welcome to the Centrify Express community.
If you're referring to this link:
Unfortunately this is a non-Centrify link.
You should be able to lay-out your PAM modules accordingly. Remember that perhaps the session PAM module does not apply here.
Please provide more info, this way we can try to recreate in the lab.
a) Version of Centrify
b) Version of Ubunty (target)
c) OS/Version of source.
They all should have Centrify and be joined to AD for this setup to work.
R.P