Xiaomi 1s suddenly can't send short messages online, and has been sending them.

It may be that some applications in the other system interfere with the normal operation of the system, especially some programs that have obtained root permission. Therefore, for the security of the mobile phone system, please do not use root permission at will. It is recommended to back up the data, enter the recovery to clear all the data (turn off, press and hold the volume increase+power on button to enter the recovery), upgrade the mobile phone to the newly developed system with a wire brush, and temporarily do not install the application that requires root permission to see if it can be restored to normal.