I had a similar problem when I first got our 2015 33.3 coach last spring. I did not have the parking brake set and I did not have it in neutral. I felt a bit silly after I finally was told what to check.
Also, did you check to see if you turned off the chassis battery main disconnect switch when you got home and maybe did not turn it back on when you tried to start it again ? Just a thought. Hope you get it figured out .