Ok so I just got it to work, after looking at the thread and seeing some people in the same boat as me while others were having no issue, I decided to try something new. I restarted the quest and chose the dark side options for the first two guys you go to on the list(my agent is almost pure light side so I had previously been selecting light side) and this time when entering the casino it triggered. I'm not sure if thats actually the trigger, but if those who are still having trouble want to test it, or if they're already dark side and still having issues then obviously that would debunk my current theory. Regardless hope it helps and good luck to those of you still having issue!