I tried the Firmware Updater on a laptop with Windows 10 (build 1703) and it is working fine.
Printer was recognised on COM3 and firmware flashed.
Try to connect the printer and in safe mode delete all the "Prusa" drivers, unplug the printer. Then boot to "normal" mode, attach the printer, let Windows do its business and then install driver's package from us.
Let me know
P.s.: In devices I see the printer as "3D Printer powered by RAMBo (COM3)