What is the ruling on one who forgot to recite Al-Fatihah in a silent prayer; and must he make up the Rak'ah?

The jurists have differed regarding the ruling on the congregant reciting Al-Fatiha behind the Imam. The preponderant view, in our opinion, is that it is obligatory for him to recite it in both silent and audible prayers. However, one who did not recite it is not required to make up for it if his action aligns with the view of one of the Mujtahid scholars, especially if he is following someone who holds that it is not obligatory. As for one who forgot to recite it, and he is among those who hold it to be obligatory, he should perform an additional unit (rak'ah) after the Imam’s salutation. If he remembers or doubts before bowing with the Imam, he should lag behind to recite it; otherwise, he should follow the Imam and perform an additional unit (rak'ah) after the salutation.