When we had this happen at our shop, As was said before it was usually rusted and dry. We had the most luck with spraying all the hinge points with WD40. Operate the steps several times. Let them sit overnight. The next day spray again with WD40. The WD40 is more of a cleaner and dissolver than a lubercant. After a couple of weeks, Lube the steps with a light spray grease. Keep the steps lubed in the future. about every six months give a good dose of WD40 to break up the grease buildup. You will have to lay on the ground to be sure you get to all hinge points. Make sure you do the motor clevis and linkage.