Xiaomi's mobile phone suddenly lost all the previous text messages. What happened?

It should be caused by switching the system. I met it twice. 1 time is no problem. I backed it up the day before. I switched the system once last night. I found that there was no text message this morning, which was the last backup. I didn't have a text message for more than 0/0 days before the Chinese New Year, so I was extremely depressed. If it has been backed up before, it can be restored. If it has not been backed up before, it cannot be restored.