Error code F5

We sincerely apologise for the inconvenience caused.
Please reset the device and then charge it for at least 30 minutes using a standard household power socket. Afterwards, check whether the device has returned to normal operation.
To reset the device: simultaneously press and hold the DISPLAY and USB buttons for 10 seconds. The display will briefly show “8888”, then return to the normal interface — this confirms the reset is complete.