It's not normal at all. Check that, when buildings don't show, you have BOTH those menus in the "Addons" menu:
- Addon Manager
- Couatl powered addons
You said you purchased the scenery today but, are you using a current installer, and not some old installer you might had downloaded in the past ?
In any case, I see you are italian, you can contact via email, I can reply to you in italian, if you whish.