What is the ruling on shaving pubic hair, and is the Hadith, which means that the prayer of one who has not shaved their pubic hair for forty days is not accepted, an authentic Hadith?

Shaving the pubic hair is a Sunnah, and it should not be left for more than forty nights. There is no mention that the prayer of one who neglects to shave the pubic hair is invalidated, unless it prevents water from reaching the skin during purification.