You need to have a package (room + tickets) through Disney in order to get the dining plan, in most situations. The exceptions would be if you are staying at a DVC resort on points or if you are an AP holder booking a room on an AP room-only discount. If you purchased your tickets from a 3rd party or if you purchased them from Disney, but not through CRO, then you cannot get the dining plan. No big loss because it isn't a money-saver when you pay OOP for it.