Answer: He left the Catholic Church when the pope would not grant an annulment to his first marriage.
Step-by-step explanation:
Henry VIII was married to Catherine of Aragon, but had been unable to produce a male heir to the throne with her. She had a stillborn daughter, a stillborn son, and two sons who died within hours or weeks after their birth. She ultimately had a healthy daughter, Mary (who later would become Queen Mary I of England), but Henry wanted to end the marriage to her and begin marriage with a new wife, Anne Boleyn.
When the pope refused to grant an annulment, Henry VIII broke away from the Roman Catholic Church and, with the help of Archbishop Thomas Cranmer, established himself as head of the Church of England.