The module Configuration Engine is currently unmaintained.
Either the feature is obsolete, or the feature is updated such way that webmin no longer interfaces correctly.
The current webmin module seems to support CFEngine 1.x whereas the oldest supported version is 2.x
The Configuration Engine module configure the CFengine program, for checking and maintaining various system-administration settings.
The software can be installed as
cfengine3 using the Software Packages module.