Recently I've noticed that Nolan doesn't really know what to do in the sand box. I'm not sure why, he generally walks around watching other kids (sometimes with his hands behind his back like an old man) or pushes trucks around in the sand.
It's funny because he plays with his sand box in the yard just fine, filling up containers and dumping them
Maybe he needs to bring his trusty blue shovel with him. He loves the sandbox at the playground, but doesn't really 'play' in it.