Bluetooth pairing is not working.
I cannot get my micro:bit to pair with my mobile phone.
I cannot get my micro:bit to pair with my tablet.
Since I used MicroPython, Bluetooth pairing no longer works.
How do I restore my micro:bit to factory defaults?
The Bluetooth pairing feature is part of the DFU – Device Firmware Updater – and the DFU is only present in .hex files that were generated from Blocks, Touch Develop, Code Kingdoms or PXT. The MicroPython language does not have enough memory for Bluetooth use, so the Bluetooth is disabled, and no DFU code is present in any .hex file generated by any of the MicroPython editors.
Use one of the non-MicroPython editors to write a simple program, and flash that .hex file onto your micro:bit using a USB lead. This will restore the DFU firmware upgrader, and the three-button entry into pairing mode will work again.
Note that when you flash your micro:bit over a USB lead, it will remove all record of any previous Bluetooth pairing on the micro:bit itself. The phone or tablet you used will still remember the pairing, but this will now be invalid. You should follow the full Bluetooth pairing sequence as normal from this point, before you can then re-flash .hex files to your micro:bit over Bluetooth.
Here is a link to a very simple blocks program, that if you press the COMPILE button to generate a .hex file and flash this file over the USB lead to your micro:bit, it will restore the DFU firmware upgrader and allow you to use Bluetooth pairing again.