I can't answer for sure about your particular RV. However, I used to have an old Holiday Rambler motorhome and it would not start with the antenna up. It would also sound an alarm as soon as you turned on the key. In my Miramar you don't raise an antenna so I'm not sure if the alarm is still a feature or not on some RV's.
My suggestion is to just raise your antenna and try to start the engine.