ArduPilot APM 2.8 not arming

I have Ardupilot APM 2.8 and Avionic RCB6i transmitter. I have bounded the Avionic RZB receiver to transmitter on channel 3. But when I pull the ideal throttle to the right, which is standard way to arm the controller, it didn’t arm. What am i doing wrong? Any ideas

Maybe you have to connect our receiver to the FC or to switch both on or also the transmitter on. Who knows.
If you want to get help, you first have exactly to describe your setup, which firmware and which settings (param-file) on the FC, how rx is connected to FC, is a GCS connected, if yes SW Version.
If your FC is not arming than mostly some settings are wrong.