There is no need to use the C4D importer plugin as you can import the native c4d files directly into After Effects and access to multipass using Cineware.
Are you getting your importer from the latest C4d install?
you can find it here on mac
/Applications/MAXON/CINEMA 4D R18/Exchange Plugins/aftereffects/Importer/OSX/CS_CC
not sure about pc but I'm sure it's similar.