Often when only one axis is not working, it can be fixed by trying one of these things:
- Make sure you uninstall vJoy and Smartpropoplus if you have them. Their driver messes with things when connecting via USB.
- Make sure you don't have any other joysticks/controllers connected, that might cause a conflict.
- Make sure you have "Heli" selected as model type on your radio. ("Plane" generally doesn't work very well).
- Perhaps you can remap the output channels (in the menu of the transmitter) so that it sends to another channel.