If the micro:bit is connecting as a drive called MAINTENANCE instead of MICROBIT, then you are in the maintenance mode provided for updating the DAPLink interface.
The way you access maintenance mode is by plugging in your board to your computer's USB port while holding down the reset button.
If you try and flash a normal hex file to the micro:bit whilst in maintenance mode, it will fail and result in a FAIL.txt file being created with the following advice
The hex file you dropped isn't compatible with this mode or device. Are you in MAINTENANCE mode? See HELP FAQ.HTM
Clicking on the associated HELP_FAQ.HTM will direct you to instructions on how to access normal mode:
To leave maintenance mode, unplug the board from USB, make sure the Reset button is not pressed, and plug the board back in.
The board should now show up with the correct name (for example, MICROBIT). If this fails to work, please update the micro:bit firmware