The cable I have ends in a female DB9 and physically connects to the radio fine.
Right, but the physical connection isn't enough - the port on the D700 is not wired like a normal serial device intended to connect to a PC, which is the problem.
One thing I observed was when I entered the Radio Download menu it keyed my Flex 6600; there's no reason for that as the Flex doesn't have that COM port in its CAT list. I've shut down the Flex and all other apps and rebooted the computer with the TM-D700 on and the FTDI cable connected at both ends. This time the Radio Download action in Chirp resulted in the fan coming on for about 2 minutes on the TM-D700, and then still no results on the screen.
The act of scanning the ports on the system may cause the DTR pin to assert, which can cause some radios (i.e your Flex) to go into transmit mode. However, it should be brief.
If the fan comes on on your D700, you're probably also making it transmit, which probably means it's in TNC mode or something.
After my last message, I pulled out my D700 and confirmed that it is indeed a gender changer needed to talk to a DCE serial port (i.e. on your PC), not a null modem. The radio has a male port wired DTE, which is not normal for a peripheral. So your cable, unless it's intentionally wired wrong for a D700, is probably expecting another DCE device (i.e. has a NULL modem in it for talking to another computer). But, if it really is wired for the strange configuration on the D700, then you need to make sure your radio is ready for serial communication (i.e TNC and KISS disabled, etc).
Could you tell me how to generate a debug log? I've enabled Developer mode but that menu is still grayed out even after restarting Chirp.
The first thing you should do is disable developer mode and restart. Developer mode is intended for developers, not users, and you should not be running in that mode.
Next, reproduce the issue and capture the log. Instructions are here:
https://chirp.danplanet.com/projects/chirp/wiki/How_to_report_issues
I'm not sure what "that menu is still grayed out" refers to, but it's not anything related to the debug log, that I know of.
Please do *not* send the debug log to the thousands of people on this list and instead open an issue per the instructions above and I'll at least let you know what the log indicates, if anything. My D700 just now connected and downloaded immediately without any problem, so I think CHIRP is likely not the culprit here.
--Dan