Before doing that, try shorting the center two pins on the unpopulated 0.1" connector labeled PROG. Pin 5 is MCU reset and pin 6 is ground, so it will hold the microcontroller in reset. If it's an MCU issue holding it in reset should cause the device to pop up on your computer as the FTDI chip will be able to connect. If it doesn't show up, it likely is the FTDI.