Can't Update firmware - CUBE

I have a black CUBE PixHawk2. It contains 3.5.5 firmware and I tried to update it. I can connect using MP and read and write parameters, so I know I have the correct COM port, but when I try to upload FW, it gets hung at the “determining board type”. When I go into TERMINAL and try to connect, is reports “cannot open COM port”. I even tried APM Planner in order to load the latest code, but that doesn’t work either. Ideas?

When I use update firmware manifest, it gets to the “scanning com ports and hangs”.

Uninstall Mission Planner and re-install it. It will fix possible device driver issues

I tried that, but it didn’t work. Strangely, I used another computer, running the same version of Windows and it DID work.

Start MP, connect to the FC, wait untill params have loaded. disconnect, go to Install Firmware page and press Force Bootloader. Then select your firmware and upload it.