Are you sure you're talking to the right guy? That casino is fairly crowded, you may be talking to a normal dot instead of a blinking one if you're relying too heavily on the map. --- The world you see with your eyes may well differ completely from the one I see with mine. There are as many worlds as there are observers-Doreen, Chrono Trigger
Try everyone in the casino. A guide says it should be the 'bartender'. iirc now he's next to the guy that will sell you chips and stuff for the minigames.
If you're blinking light is flashing for someone on the other side of the room, it may actually be for a separate sidequest. Who knows?
Or perhaps something went wrong and you failed to actually accept the quest from the spice dealer guy. I don't know.. if you're going for the platinum trophy you're just going to have to try whatever you can to troubleshoot. If not, I suggest skipping it.