What Causes Lack Of Bleeding Despite Taking Mifepristone And Misoprostol?

My wife is pregnant 5 weeks & 3 days. She took 1 mifepristone tablet on 16th march (3 pm) and two two tablets of misoprostole on 18th march (7 am & 3 pm respectively). However, today (19th march), yet she has no induced pain & no bleeding. Please guide.