Xiaomi mobile phone 2 received a text message after updating the system, and there was no sound.

Mine won't. If you do this, it only means that you made a mistake when upgrading the system. In this way, the system may lose the original function of your short message. I suggest you upgrade again. Another point can illustrate this problem, that is, the recovery after backup is still the same, which probably means that your system has lost some system files.