In case of secondary amenorrhea who fails to get withdrawal bleeding after taking Estrogen and Progesterone, the fault lies at the level of
Secondary Amenorrhea
Definition:

In women who have menstruated previously, no menses for an interval of time equivalent to a total of at least three previous cycles or 6 months
Uterus must contain a functional endometrium that can respond to the actions of ovarian sex steroid hormones, estrogen and progesterone
When estrogen and progesterone both were given and no menstruation at the end, the pathology lies in the endometrium

Causes:

Tuberculosis, Schistosomiasis
Postabortal or puerperal curettage
Asherman's syndrome
Pituitary
Endometrium
Ovary
Hypothalamus