Electrical issue

that depends on the converter ?

did you store the trailer all winter in your driveway with it plugged in and the NO battery ?

NOT a good idea

I had the battery on a trickle charger all winter. The battery won't charge, I tried putting it on a charger.

So if I don't have a fully charged battery hooked up, the electric won't work even if it's plugged into house current?

Often the converter is mounted to the power distribution panel chassis, in a separate compartment. If it's not there, it would probably be a deck mount converter and that could be placed most anywhere.

Without the converter or something else charging the battery, it's not surprising it's dead. It may not recover fully (or at all) with charging; lead-acid batteries don't take kindly to being fully discharged.

Where is the converter? Can I disconnect the battery? The battery is dead

Very common , usually involved one or more of these things
Battery disconnect is used, battery not connected
Bad cable
Converter is bad
40 amp automotive auto reset thermal breaker for battery is bad, located under frame near tongue, in main positive cable line

Battery voltage has dropped to almost nothing. Could be converter is shut off, so start there. Check output voltage of converter on 12 volt terminal strips. If it shows over 13 volts, then check at battery posts. If it doesn't show the same there, look at the connecting wires.

In my case the negative feed to the battery at the converter terminal strip was loose, preventing the battery from charging.

Battery is dead. Is it charging? Did it get hooked up backwards?