a typical reason for 12v not working, when the 120v does, is that the owner reversed the battery wires, setting off a resettable inline circuit breaker.
they are usually located along the trailer's tongue, between the battery and the front of the trailer. there's usually a little black button to reset with.
otherwise, there's usually a plunger switch that the sink top pushes down onto, when it's flipped up, during setup.
if the plunger switch is malfunctioning, the 12v stuff doesn't work.
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC