Sometimes when you install a new queen in a nuc they don’t always release the queen on their own. There is a layer of candy (similar to fondant) that keeps the queen trapped in her cage and the bees eat through that to release her. Strong hives can accomplish this in a day or less. For young, small nucs this can take more time and sometimes we step in to help them out. Here is how we released a queen from her cage into the hive.
You can see her come out of the cage at 0:49.