UPDATING THE FIRMWARE IS NOT SUPPORTED BY MONOPRICE
Monoprice may tell you that you have voided your warranty if you attempt to or successfully update the firmware.
PROCEED AT YOUR OWN RISK
Motion Controller firmware has been temporarily removed.
Too many people experiencing incomplete firmware updates which leave the printer non-functional. The fix is to use a microSD card that the printer accepts.
Updating Monoprice MP Mini Delta Motion Controller Firmware
A much longer than necessary video but it shows the complete steps needed to successfully update the Motion Controller firmware using the included microSD card on the first try.
YouTube link: https://youtu.be/zAj9wqvPNfA