AI have made white modeling chocolate several times , it has turned out and worked perfectly every time. I decided to make a dark modeling chocolate in order to mix with my mmf to help get a good black fondant. It has been sitting for 9 hours and is still really soft. I know it needs to sit over night, but when doing white it is usually harder by now. So my question is is this normal with dark chocolate, and if not is there something I can do order to fix it now?

I used 2 cups of chocolate chips and 1/2 cup of corn syrup in which I found in a website.