Protein balls can have a bit of trouble sticking together when there are too many dry ingredients and not enough wet ingredients. In other words, you need to have a well balanced recipe in order for the balls to stick together. In this recipe, the peanut butter, pumpkin, and maple syrup all help to bind the protein balls together. If your balls end up a bit crumbly, just add a tad more maple syrup or pumpkin to the mixture to even it out.