We have the same MW. They work differently than the typical household type. You need to press the time button first, then enter the time, then the start button. Nothing will happen if you don't and it will seem as if it is broken. I think the other functions are the same deal, but I'd have to go out and look at ours.
In a household type, all you do is enter the time first, then hit the start button. Not sure why they don't make RV ones the same.
I found I had to stop and consciously remember what to do first before I tried to get it to run. A couple of seasons later with this MW, I'm finally getting it right the first time, lol...
If still having difficulty, not that anyone should have to (I haven't), but you *could* always read the manual. Then, if even that doesn't help, there must be something faulty.