Often when only one axis is not working, it can be fixed by trying one of these things:
- Make sure you don't have any other joysticks/controllers connected, that might cause a conflict.
- Make sure you uninstall vJoy and Smartpropoplus if you have them. Their driver messes with things when connecting via USB.
Also, if during calibration the automatic stick detection gets it wrong -
Keep an eye on the little circles as you go through the calibration.
You can manually click on the circle that you see is the correct one for each stick (instead of clicking "OK")