OSD configuration and firmware is not uploading. To config and update OSD firmware I used this video tutorial (link is mentioned). The error I am getting is “Failed to talk to bootloader”.

Connect the OSD to the FTDI.
Connect the FTDI to a USB port.
Launch the OSD config tool.
Select the correct COM port.
Push and hold the RESET button on the OSD.
Click Connect in the config tool and release the reset button.

If you still get the error message and if you are using Windows 10, verify that you are NOT using the Windows 10 "Universal Com Port " driver v10.1.1

This driver breaks CP210x communications and you need to revert to version 6.7.5.

You can download the driver here: https://www.silabs.com/products/development-tools/software/usb-to-uart-bridge-vcp-drivers

One other point: Instead of using the old and outdated ArduCam firmware, I recommend using MWOSD.

The firmware is much better and there is a build for Pixhawk (PX4) and APM 2.x(MavLink).

You need to register the GUI, but it is well worth the 1.99 pounds sterling.