If you can't get your Microbit to pair or connect with the Chromebook, you may need to update the firmware.
Firmware is software that is embedded in a piece of hardware. Remote controls, printers, coffee makers, and MICROBITS all contain firmware and sometimes it needs an update.
Download the newest version of the firmware here.
Unplug your microbit from the computer. Then plug it back in while holding down the small black reset button on the back, like this:
3. After doing this, you should see the microbit show up as "MAINTENANCE" in your Chromebook Files window.
4. Drag the firmware file that should now be the most recent thing in your Downloads folder onto the MAINTENANCE icon and the firmware will automatically update.
5. The microbit will self eject. Unplug it and then replug it in and you should be good to go with the pairing process.