Dear Jesus Saves:
Thanks for writing! So sorry to hear that you had a different experience than most when you made this recipe. I have been making this for more than a year without any problems, so I am wondering what happened. A few questions for you:
Did you use a scale to measure out the ingredients? It is so important to make sure you use grams (NOT teaspoons, tablespoons or ounces). For example, if you were to guess on the clay and used over 5 grams, it may turn clumpy and not mix very easily.
Did you make sure the mixture heated to at least 120 degrees?
If you followed the recipe exactly as written, I don't know what happened. I have experienced similar events when I try to follow a recipe from a magazine and even though I do exactly what the recipes says, it sometime just does not work. Perhaps you can save it by adding in some water and reheating it.