let's first try to calibrate it:

1. remove safety key
2. press and hold the speed+ and stop keys at the same time
3. Put the safety key in/on and release the keys
4. press stop once
5. hit the incline + arrow and let the incline go the whole way up and down
6. remove safety key and try

if this doesn't correct the issue follow the steps below:

Sometimes incline motors will get frozen in position and need broke free.Take 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. run the incline up and down with the screw still off( laying the treadmill on its side may make this easier). Once it goes up and down (hold the screw so it goes in and out) reattach it then run the calibration described above. If it was just stuck it should work fine.

If these instructions do not work to fix the incline motor
check your main harness running down the right leg for breaks in the wires or a loose connection if nothings found you can switch the red and black wires on the incline motor terminal block and see if it goes down. If it does you know you are only getting voltage to one side of the motor. There is a schematic under the motor hood that tells you what the voltage should be when you press the up or down keys. Use a multi-meter to see if you are getting the correct voltage coming from the console to the motor control board and then from the board to the motor. If no voltage from console-replace console if you have voltage from console but not from board - replace board and finally if you have voltage from console and from board replace motor. You will need to test the voltage both when pressing the up key and the down key.