I have the Kenwood TM-D700A powered on and connected to my computer via a BlueMax49ers FTDI cable. Chirp correctly identifies the COM port confirmed as the FTDI cable in Device Manager. The Radio à Download from Radio menu selection opens the popup with the COM port, make, and model selections all available. Clicking OK results in the FTDI lights blinking for a few seconds and then nothing. What’s missing where there’s no download of the radio’s memory, which has most all memory slots filled with something?
Hard to say without a debug log (in a bug). I don't think you're missing anything, assuming that the radio is set to be controlled by the PC and you have proper cabling. The D700 is weird because it has a male DE9 on the front. IIRC, you need a gender changer but *not* a NULL modem to interface it to a normal PC DCE serial port. The hang you're seeing is the driver trying to quickly probe the baud rate of the radio, and I'm assuming, getting no response. But, if your cabling is indeed right a debug log will tell us if something else is happening.
--Dan