I asked and they confirmed earlier today that the investigation was indeed requested by their provider, and not conducted by themselves. On this case, their hands are tied. Every casino's hand, to be precise. Be it a young and small casino or the big ones that's been here since the inception of crypto casino, when a provider asked for an investigation, most likely than not, all they can do is just like what you can do: wait.
I understand that this is frustrating, but perhaps give them some more day. And as inconceivable this idea might sound to you, I'll suggest to wait for 14 working days. You're in 10 days today, it's about 7 working days, if I calculate the calendar correctly. But, given 14th working days [your luck must be... at the all-time-low] will happen to be on Christmas Eve, I'll try to reach them again on 20th of December, see if they probably already got a greenlight from their provider but someone forgot to update the status, suppose the situation doesn't resolve itself before 20th.
I hope it's as you wrote. Thank you.