我个人觉得是错在连接词then了,这个句子应该是因果联系的,因为我起床晚了,所以我错过了公车,但是because和so不能同时出现在一个句子中,所以可以说Because I got up late, I missed the bus.又或者I got up late, so I missed the bus.
Because I got up late, I missed the bus. I got up late, then I missed the bus I got up late, so I missed the bus I missed the bus because I got up late. 修改了一下,供参考。希望有帮助