ArduCopter 2.8 Disconnect as soon as i turn my Transmitter on

I connected my FlySky FS-iA10B Receiver to my new ArduCopter 2.8 .
All works fine. But then i turned my FlySky FS-i6X on and the ArduCopter disconnects from my Computer.

“new” ArduCopter 2.8?
That’s the old hardware running the very old firmware. Please return it and get a pixhawk. I don’t think that old hardware supports PPM

Of course APM FC’s support PPM.