I just added the coco fiber to her KK and added in a water dish and put some moss around it to keep up the humidity, she did the rest. It didn't take mine long, but maybe she was grateful for having any amount of sub because I'd seen her at the LPS for several months and she lived in a deli cup with a small stick, no room to move at all. Yours just might need some time, my C. fasciatum still hasn't made a burrow yet either, but you could try to dig out one of the corners to give her a starting point, I've done it before with success.