RC_OVERRIDE_CHANNEL not working in mavproxy

hi , currently im using mavproxy to control my quadcopter. But somehow, i can't override the channels using RC_OVERRIDE_CHANNEL command which is "rc all 1000". The quadcopter seems to have no response at all when i execute this command using mavproxy connected using USB...... Any advice? Thanks

Start by reproducing the `rc all 1000` command in MAVProxy over the USB connection and inspect how `RC_OVERRIDE_CHANNEL` is handled. Check whether the quadcopter receives the override and document the conditions needed for the channels to respond.

Written by the indexing model from the issue text.