Your problem doesn't have anything to do with any of the issues reported here, since you *have* both the Couatl and Addon Manager menus, it means everything is working, all the suggestions are only relevant if you don't have one of the menus.
It seems that you have removed the KLAX folder in the Simobjects folder, reinstalling the scenery will fix this. Use the current version of the installer, not an older version you might have, if unsure, download it again.