As I've said, just disabling McAfee is not enough, you need to reinstall the scenery again, because McAfee blocked the needed file from being installed when it was active.
Try to do this after rebooting Windows, and check the antivirus is still disabled after the reboot.
At the end of the installation, when you launch FSX, check that you see both the "Addon Manager" and the "Couatl powered plugins" menus under the "Addons" menu.