Like Cayugad said, firing a couple of dry caps before loading your muzzleloader will certainly help solve this problem. Another step you can take to make sure this doesn' t happen again, is to load the gun, unscrew the nipple and sprinkle a couple of loose grains of pyrodex in the nipple chamber, then screw the nipple back in. Don' t put much below the nipple- just enough to send the spark all the way through to the main charge. I guarantee that your gun will fire on command if you do this.