Pixhawk Telem, but no control; Ground Rover + Windows

I’m new to the pixhawk, but as part of a project I’m trying to adapt the following example code to Windows (would use Linux but cannot due to various project constraints)

I’ve loaded firmware to the Pixhawk via QCGroundControl, and configured it as a rover, and I seem to be able to read telemetry data using my adapted version for Windows 10 (see: GitHub - swatza/Autopilot_Interface_Win: For Windows wip) however, I cannot for the life of me figure out how to get offboard mode to enable properly and be able to send mavlink messages to control vehicle motion.

Have tried using both the usb port and the telem 2 port with an FTDI cable.

(I apologize if this should maybe be under flight controllers)
Any help or direction would be much appreciated!

Can you provide more detail? Did you get anything working over mavlink? What happens when you try switching to OFFBOARD?