This site is being deprecated.
Please see the official X‑Plane Support page for help.
Are you using custom button assignments on your yoke or joystick? Double check that they are using flight_controls/pitch_trim_up and flight_controls/pitch_trim_down.
If it is for a custom plane, have you set the detents in Plane Maker? Here is the section of the manual explaining flap detents and showing where to find the settings in Plane Maker.
This site is no longer being actively maintained.