Specs say it may have a 65 amp 12 volt power converter, battery charger. It should charge the battery lickity split when plugged into shore power or a generator.
Tongue jack may work when the TT is connected to the tow vehicle and the engine is running.
Circuit breaker on main 120 volt circuit breaker panel supplies the charger with power.
12 volt fuses on the 12 volt fuse panel. They may be 30 or 40 amp fuses.
If you have an inverter/charger installed, there may be a fuse or circuit breaker between the charger and the battery.
You may have a 12 volt power switch near the entry door that is turned "OFF".
There may be a battery disconnect switch near the battery that is "OFF".
There are other possibilities that are less likely.
Get a cheap digital voltmeter from your local hardware store and follow the 12 volt power from the charger to the battery. Charger should provide more than 13.0 volts after charging for a few hours.
Be sure to fully charge the battery for 18 hours one way or another soon. Storing a lead acid battery in a discharged state can kill it quickly.
Dutchman Kodiak Cub KD176RD 2018
Nissan Pathfinder 2015