Welcome to one of the most discussed problems on the forum. There are a lot of things said about what I expect are your steps(Kwikee)and so very well documented on these forums. If the DW is stuck inside that might be good but your outside and that's bad.
Joking aside, if the steps are stuck in the retracted position at least you can move if you can't fix it.
I would try to remove the cotter key in the clevis pin, control arm and then do my testing. When the clevis pin is removed there is nothing holding up the steps. Something tied around the steps or under the steps to prevent them from extending an ruining your day are necessary.
With that done it is easy to check voltages and determine your problem. If you do not have the manual for your steps, search on line for Kwikee Manual #888. It is very comprehensive and you'll be able to isolate the problem. Fixing it is another thing. Look for an added on fuse holder anywhere there is a place to get to a constant 12 volt source.
Good luck and use the Search engine here on the forums. Lots of stuff.