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 to check whether normal operation is restored.
To reset the device, press and hold both the Power button and the USB button simultaneously for 5 seconds. The screen will briefly turn off and then relight, displaying the battery percentage and other information — this confirms the reset has been completed.