Can you post/send me a screen shot of your network? I should be able to debug it from there.
OK - I figured out what's going on. There's a bug in the Pool Span node, where it requires 3 or more dice to work instead of two.
I've fixed it, but in the meantime you can just use the SPAN node which takes two numeric inputs. Here are two examples with the fixed POOL SPAN node on top, and the SPAN node on two dice on the bottom. Both histograms are the same.