I am not sure why it did not work. Last time I did this cleanse it took a whole day to work, and this time, it had not happened after two days. I think senna is an herb, but dangerous, I don't think it is smart to forcefully stimulate the nerves that regulate bowel movement. And it also states to stop using if you get any cramps, etc. I have heard MANY users say they get cramps. that means to stop usage.