never fail to V

원래 문장이 They had light the lanterns when a bell rang in the evening. If they failed to do so, they were fined heavily.인데 문제에서 문장을 바꿨어요.~ If they never (succeeded / failed) to do so, they were fined heavily. succeeded와 failed중에 답이 succeeded라고 하네요. 설명부탁해요