I had the EXACT same problem! I discovered that sometimes the prong at the bottom that is supposed to puncture the Kcup didn't actually make a hole. I looked at the Kcup when I had the problem and there was a small dent, but no hold. I punched a hole with a knife, put the Kcup back in and tried again. It worked perfectly. I hope I don't have to keep doing this with every cup.