Doug is exactly right. My last coach, the power steps motor went out and had to be replaced two different times.
Something about electric motors out exposed to the elements like that, with time they just wear out. On last coach, I replaced the step motor twice, the awning motor, and hydraulic jack motor over the course of about 10 years owning that rig. Never had any trouble with motors that were inside, protected from the elements.
You might get lucky and find its something jammed up, or the door sensor, but I'm betting its the motor. They aren't that expensive, and you can replace it yourself (I did both times). Can be a challenge getting new motor lined up and all those spacers in place, but it is doable.
Oh, and yes, be very careful when working with those steps, like already said. They can take a finger off if you aren't careful.