Welcome to the Centrify Express forums.
You may have a version mismatch.
Ubuntu 16.04 support was added with 2016.1 (5.3.1) and you're running version 5.3.0
Make sure that both the base agent and adbindproxy are at the latest versions. (5.3.1.x)
FYI on naming, back in the spring, due to the Badblock vulnerability and other complexities we immediately ended the distribution of Centrify-enhanced Samba. The integration that you're referring to is the Identity Mapper only (adbindproxy).
If after upgrade, the problem persists, please let us know.