Almost everything in Airstreams works from 12 volts. Three or more things could be causing your problem.
1. On/store switch in the store position. Look for a rotary switch with a lever. It may be marked on/off or use/store, or something like that. It should be in the on position. That switch kills all 12V
power to the trailer.
2. Bad, discharged or missing battery, and/or
3. Bad or missing converter/charger. This box provides 12volts when connected to AC to operate 12v
stuff and charge batteries.
I don't know anything about the specifics of your trailer, so if these general suggestions don't help maybe someone who has one like yours will chime in.