Duphastone tablets are supposed to take for last 14 days of cycle. Then once you stop the medication you will get period in 5-6 days time.
As it is hormonal
problem; response varies individually , 2-3 days difference may occur. But you will get your period as bleeding is not physiological menstrual cycle but it is withdrawal bleeding.
If you still dont get periods, you are supposed to consult gynecologist for thorough screening.