本句缺少一个主语 ,I ,He 或者they
I didn't know you like that song.我不知道你喜欢那首歌
He didn't know you like that song.他不知道你喜欢那首歌
They didn't know you like that song.他们不知道你喜欢那首歌
能解决您的问题吗?