never fail to V 문법 질문

원래 문장은 “They had light the lanterns when a bell rang in the evening. If they failed to do so, they were fined heavily.”예요.
문제에서 “If they never (succeeded / failed) to do so, they were fined heavily.”로 바꿨는데 답은 succeeded라고 하네요.
왜 그런지 설명 부탁드려요.