Unclear antenna tracker configuration (in proxy mode)

I am trying to follow the wiki instructions to setup an antenna tracker, using a pixhawk (driving the antenna tracker servos). Firmware is installed and configured.
I used the connection scheme of the wiki with a 3DR radio link between the vehicle and the antenna tracker’s pixhawk. And then I connect mission planner via usb cable to this pixhawk.
I get in mission planner the icon of the antenna tracker on the map, I get all of the config menus of the antenna tracker.
But I do not see anywhere the vehicle as if the antenna tracker was not connected to any vehicle.
I tried CTRL+X to switch vehicles on the MP display but no joy.
What did I miss ?

Problem was solved through a reinstallation of the firmware on the copter side! (not on the antenna tracker side); The pixhawk used on the antenna tracker could not receive for som strange reason the mavlink messages sent from the copter.

This issue is thus for me closed.