Ovidiu Macek (the blackjack dealer) of the Prancing Nymph doesn't seem to want to start a game of blackjack. To my understanding of the rules - which might be wrong - he's supposed to sit down once you tell him to start a game. He sits down for maybe a second or two, then stands up again. He doesn't seem to respond to "start", the bet amount or "bet" in chat while he's sitting or standing.
I imagine not many people use this npc and there are a lot of alternative dice games you can play using the commands, but I think it could be nice for a bit of variety. Could also be that I'm misunderstanding how to properly start a game also, but if not the npc is unfortunately bugged.