Did you use any bonuses? If so, I’d examine the terms with a magnifying glass and make sure you didn’t play any games you shouldn’t have or anything that might give them a reason not to pay.
Personally, I don’t play there and probably would never choose that casino to deposit at when they’re are far better choices for RTG like ClubUSA Casino for instance. 
Hopefully you’ll get it. Did you ask what the problem is?
I’d be careful on doing chargebacks since it can haunt you if you like gambling online. That should be the absolute last resort. I wouldn’t even think about going that route so soon.
Congrats on your win and let us know if you get it.