Your air conditioner doesn't require 12v
power, but all the lights in your trailer do, as well as the water pump and the exhaust fan above the cooktop and in some of the roof vents.
Your battery may be discharged or disconnected or bad. One possible explanation is that the 12v
converter isn't working, so it neither charges the battery nor powers the 12v
system. Another problem is that one of the main 12V fuses has blown. Have the battery tested on its own. Any competent RV service tech should be able to troubleshoot the 12v system, yours is very straightforward.