There are a few points that might lead to a fix.
One is that the power for both items comes from the chassis side of things. There often are two groups of fuses/breakers, one for RV things which Winnebago adds but another for the normal truck items like horn, lights, turn singals, etc. So when looking for a power problem for the mirrows and step, first locate the box with auto type things? That would often be under what passes for a hood on many RV. There may be one or more that have failed.
Both models of your Meridian seem to have the same wiring but I took this snip from the 39Z model as typical.
Click this snip to get a better view and idea of what I am thinking may need checked.
If not finding a fuse, you can also test for power and ground on the various parts of the step system. I go to the one I can get to easiest first!
But is your step kill switch set right?