First thing, Take lots of pictures for reference. Take a hammer and tap the step motor, If that doesn't help Unplug the motor underneath and use a 12v battery (I use a lawn tractor battery)
Hook-up leads and see if you can activate step ( be sure to keep your fingers out of the step mechanism ) Reverse polarity to open and close. If that doesn't work then knock lynch pin out
( It will be tight under tension) Be sure steps are moving freely. Remove motor and take apart gear box look for 3 plastic type plugs. These are window regulator plugs available at Napa etc less than $10.00. I'm assuming you have a car window elec window motor. Generally the motor never goes bad but the plugs get flat spotted. Also assuming steps are regularly lubed. Good luck. Bill