Can you let me know what you have tried so far, so I don't repeat any steps?
Or if you haven't tried anything yet, then start by taking the motor cover off and take the screw out of the bottom of the incline motor that is attached to the screw assembly. Once you remove the screw you should be able to break the incline motor free from the position it is stuck in. Move the incline up and down with the screw still off (laying the treadmill on its side can make this easier). Once it goes up and down (hold the screw so it goes in and out) reattach the motor screw then run a calibration.
Yes, remove the screw (see my previous post)