Can't finish???? Bug making gun powder... – Secrets of Da Vinci HD Review

We have spent countless hours playing this game on our ipad, which has been a lot of fun for our entire family thanks to Apple TV... But we were about to finish the game except for whatever reason we are not allowed to make gunpowder!?!? We have all the ingredients we need, it just keeps saying something like "I can't imagine why I'd need that at the moment." This has to be a bug or a glitch or something! Soooooo frustrating!!! We have done EVERYTHING and have even spent hours going over walkthroughs about this game, trying to find what we missed, but it looks like it is just a buggy game :( Please fix this!
Review by Marshn on Secrets of Da Vinci HD.