Touch the screen of the Sony Xperia XZ3 or press one of the hardware buttons, and the phone may stop responding.
The display is frozen, and may even show only black. If this description applies to your Sony Xperia XZ3, then you must proceed as follows to correct the error:
Force restart - Press special key
1. Remove the cover of the Nano-SIM card slot. You will now see a small button next to the shaft.
2. Press and hold the power-off button with the tip of a pencil or similar object, such as a wooden toothpick.
3. Keep the button pressed until your device vibrates briefly several times.
4. Release the button - the unit will automatically turn off.
Note: Do not use sharp objects as they may damage the power off button in the Sim card slot of the Sony Xperia XZ3.
You now know how to proceed on the Sony Xperia XZ3 when the smartphone stops responding and the screen is frozen or black.