If you see the Addon Manager, but not KLAS on its lists, it means you somewhat downgraded the Addon Manager after you installed KLAS or, something has blocked the installation of the updated version (that supports KLAS).
Try to Uninstall the scenery, and (important) reply "Yes" to the question about removing the Addon Manager, then check your FS9\MODULES folder that no bglman*.* files are still there. If they are, manually remove them all.
Then, reinstall KLAS and try it.