The fact that a category doesn't show up today doesn't mean that it won't be available "tomorrow." It is most likely to show up as the cruise date approaches. There are many reasons for this. First, a big
travel agency or group may have taken an "option" on a bunch of cabins. They then have a certain time period in which to book them or return them to
DCL inventory...if they do neither, they'd be stuck paying for them. Secondly, Cat 11 is the "entry level" cabin....as cruise date approaches, if other categories aren't filled, DCL may give some of those wonderful free upgrades to fill other categories and entice people to book a cruise. Finally, there are people who book and for various reasons, have to cancel. This is most likely to occur just before the 60 day window when they would lose significant $ if they waited any longer.
Finally, while it is not applicable in this case (this far out), when I call my TA to arrange a cruise, DCL gives her 2 days to confirm with me, etc. and make payment. Reality is that this can usually be accomplished in 10 minutes, but for those 48 hours, DCL has technically taken that cabin out of their inventory...until the cruise is either booked or declined.
In your situation, most likely there is a large group which has booked a large block of cabins or done the "option on them" thing...keep checking, it may open up.