It’s possible that third-party software is interferring with your connection and causing an MMI error. Alternatively, press and hold the Power Button until the Shutdown options menu appears, and then select Restart.Hold the Power button and the Home button at the same time until the phone turns off and starts vibrating wait for it to restart.The first way to try to fix an invalid MMI code would be to restart the smartphone. We’ll cover them from the simplest method up to the more complicated ones.
Several methods exist to fix the “Connection problem or invalid MMI code” on an Android device.
