Shulchan Aruch YD 334:1 sets out the basic position that a nidui lasts 30 days after which it can be extended if the problem persists. It has to be specifically extended in order to continue in force. Therefore, if nobody does anything on the 30th day, all returns to normal.
But 334:27 suggests that a nidui continues in force even after 30 days, until it is specifically revoked. Therefore, if nobody does anything on the 30th day, the nidui continues.
Which one am I misunderstanding?