Steps stop working for 4 basic reasons. The most popular one is that their is an electrical issue - usually low battery or bad step ground wire. Step binding associated with lack of lubrication. Bad controller and lastly bad motor or gear component.
Check your battery condition, clean the ground wire connection, disconnect the step from the motor assembly and lube - while disconnected test the controller by opening/closing the door and see if the motor operates as it should. During this test if the motor sounds like it's working but you don't see the swing arm moving then it's likely you have a broken gear in the motor .. replace the gear or replace the motor - lots of threads on how to do that.