Also, it might help to make sure you use a USB 2.0 port and not a USB 3.0 or newer USB C port, my Evic VTC Mini refuses to take any firmware when plugged into a USB 3.0 port, but does just fine when plugged into a back panel USB 2.0 port, may have something to do with data speed, so a slower USB 2.0 is a bit more accurate for the PCB firmware to keep up with.