I had the same thing happen to me last December and I found that it was a dead motor. If this is the case with yours, they are fairly easy to change out. I would definitely recommend you change out the motor in the retracted position and make sure you pin the opposite end with something to prevent movement. Before I found that the motor was bad I connected power from the connector at the end of the arm coming off of the motorhome to the old motor and got no movement. This confirmed that the motor was the issue.
Dave and Deb, 2006 National Dolphin 5355 Ford V-10
2014 Nissan Rogue Towed with a Demco Kar Kaddy
Lt Col, Ret, USAF