Hmm, that´s weird. It sounds like you do everything right, keep tinkering with it! Make sure that the files are really unzipped, it happens all too often that people put their zipped folder into the aircraft folder. X-Plane must be able to see the .acf file for the aircraft.
Other than that, it should be absolutely straightforward. No installing, no registering (unless its a payware aircraft).
Good luck, Jan