IWR1642BOOST: I cannot flash IWR642BOOST with UniFlash

I want to upgrade the firmware in my IWR1542BOOST with Uniflash v4 but it doesn't open the COM port.

I selecte the device as follows:

then I select the binary:

And the COM port (matching the Class application/ User UART port):

Finally I click Load but stays forever like this:

And the console shows:

After some minutes there is a pop up window about some Python subprocess crash.

What do I need to do to flash the board?