The current CADPipe DWG Loader plugin looks for a cadpipe.ini or commercial.ini in the Windows directory (or usual Windows INI search path) where CADPipe usually installs their INI file. This INI file should have a section that looks something akin to:
[Locations17]
Cpquery=C:\Cadpipe\2007\cpquery.dll
which tells Navisworks where CADPipe's query API is located. If this can be found, the option to load CADPipe properties is enabled.
It is likely that one or more of these steps is failing and thus you cannot enable CADPipe xdata conversion. The CADPipe plugin also emits logging information if these steps fail to the usual Navisworks log which may also provide information as to why it cannot locate the necessary query API.
Hope that helps,
Jeff
Senior Software Engineer
Navisworks
Autodesk Ltd.