Can you try putting the device in bootloader mode. This can be achieved by pressing the reset button twice in a row (only twice and about 0.5s apart). One of the LEDs (BLUE I believe) should stay on and slowly pulse.
In bootloader mode, the device should be visible on it's secondary COM port.
If this doesn't work, we might need to send you a replacement board. You should be able to open a ticket for a replacement via the webshop.