If your upcoming cruise is a 5 night sailing and that ship alternates 4 and 5 night sailings, if you check the menu while that ship is on a 4-night cruise, you'll only see 4 nights of menus.
Also I'm on Mariner in December. That ship currently is on night 4, which of course today is Thanksgiving, which has a special menu. The menu right now for my cruise on night 4 doesn't appear