Must the Fajr prayer be made up if menstrual blood is found ten minutes after the call to prayer, with the strong presumption that it began before Fajr?

The predominance of probability is considered equivalent to certainty by most scholars. Therefore, if you predominantly believe that menstruation began before dawn, you are not required to make up the Fajr prayer. Furthermore, many scholars, including Sheikh al-Islam Ibn Taymiyyah, state that making up the prayer is not obligatory if menstruation begins after the prayer time has entered.