first, if you don't have a battery disconnect switch, the trailer's parasitic power drains will empty a battery in just a few days, if it's not plugged into shore power.
second, many new owners accidently cross the battery wires, when installing the battery. this trips a gray or silver resettable breaker/fuse that is along the A-frame, between the battery and the front of the trailer.
there's a tiny black button you push to reset the breaker/fuse. this will restore 12v battery power to the trailer.
or the fuse along the battery wire has blown.
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC