Hmmm...I am assuming you have tried all of the switches you can see at your entry way. Do you have a "command center" close to the door? Have you checked to make sure the bulb is good? A bad bulb sent me on a wild goose chase when I tried to figure out the light switches in my Tioga. Now, it's the first thing I check.
2007 Gulfstream Innsbruck 36FRS
2006 Palomino Puma 27FQ
1999 American Cruiser RE2000