Complex sentence: The Swatis appealed to Sardar Hari Singh, who was unable to help them but in 1841, Hari Singh's successor restored Agror to Ata Muhammad, a descendant of Sad-ud-din.
Split into simpler sentences: The Swatis appealed to Sardar Hari Singh, who was unable to help them. However, in 1841, Hari Singh's successor restored Agror to Ata Muhammad, a descendant of Sad-ud-din.