The important thing is to reference the same copy of the Kangaroo library being loaded by the version of Rhino you are currently running.
For instance, if you are running Rhino 6 and you reference the copy of Kangaroo from the Rhino 7 folder, it won’t work.
I believe the directories are usually:
C:\Program Files\Rhino 6\Plug-ins\Grasshopper\Components
C:\Program Files\Rhino WIP\Plug-ins\Grasshopper\Components
(if you first installed v7 when it was a WIP)
C:\Program Files\Rhino 7\Plug-ins\Grasshopper\Components
C:\Program Files\Rhino 8 WIP\Plug-ins\Grasshopper\Components