I've had pinning take longer. If the cakes weren't 100% colonized when you birthed them for instance. If temps are cooler... there are a number of things.

What do you have going for a fruiting chamber? While those cakes certainly need humidity, they also need regular fresh air exchange. So if they're not getting enough of that, it can delay pinning. You should be misting and fanning 4 times a day minimum.

No more dunking yet, unless the cakes are drying out.