RC OVERRIDES on PX4

Hi everybody!
I want to overrides RC channel like in this example: http://python.dronekit.io/examples/channel_overrides.html but seem that the FCU doesn’t react to my commands.

Are there any System parameters to set? My Firmware version is 1.5.5 lpe.

Thanks
Fabrizio

I am in the same boat as you. Did you get any ware with the channel overrides?