If you have Kwikee steps (more or less the most common) it is very very easy to check your door switch in the evening on a fairly new rig.
Standing outside the RV, open the door and look down below the door (Around the steps) if you SEE THE LIGHT (yellow light) then the controller sensed the door opening and turned on the step light.
If you do not see the light.... could be a bad bulb, disconnected or other non controller/switch issue, or it could be a bad switch.
Closing the door should turn off the light.
The light is mounted next to the controller, above the top retractable step when the steps are retracted.
IF the light is DIM, you may have a wiring issue or a frozen motor.
ON my coach, when new, the dang steps worked when they felt like it. I would crawl under and "Thunk" the motor a couple of times and they would behave for a while.
Finally I "Re-indexed" the motor (Basically this involves opening the transmission and moving a gear so the motor no longer stops at the same point in it's rotation, IT always stops at EXACTLY the same point due to hard stops)
So far (over six years since I did that) no further issues.