They should be on a 30-amp fuse. The fuse box should have a label.
Kwikee steps have been taken over by Lippert, but the manuals for the different models are here:
https://support.lci1.com/kwikee-steps in case your problem is more than just the fuse. The ground wire is also a frequent cause of failures, so that might be your second place to look.
I found Kwikee to be very helpful. Hopefully Lippert is too.