The Bluetooth pairing feature is part of the DFU (Device Firmware Updater) and the DFU is only present in .hex files that were generated using the MakeCode editor.
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 the Python Editor
Using the MakeCode Editor, write a simple program and flash the resulting .hex file onto your micro:bit using a USB lead. This will restore the DFU firmware upgrader, and pairing mode will work again.
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.
Keywords for search: Bluetooth pairing is not working, pair, mobile phone, tablet, python, reset, broken, micro:bit will not enter pairing mode