Well the only thing I can see is that it says “ We reserve the right to withdraw the offer in whole or on individual cruises at any time”
Presume it is a Select booking.
This seems to be happening a lot on the newer ships Iona and Arvia. They are aimed at the new younger cruisers, some of whom have no wish to dress up on holiday. It is a very different vibe on these ships, much more to some people’s taste.