When you look at the Motor section of the Model Menu, you can set a switch to activate or deactivate the motor function. When it's "OFF", the motor goes to the position it's set to. Check to see how it's set in the Motor function. When you turn the motor function "ON", then the slider or other control will operate the motor.

You likely will either reset the motor function, or you may need to see if it's set to "normal" or "reverse" in the servo reverse section of the Linkage Menu.