Sounds as though the battery was in a low state of discharge prior to you using the TT. Was the TT connected to shore power before you left on your trip ? If the battery was not "fully" charged & low when you left, that answers the question. If a battery is low in the beginning, your TOW VEHICLE will not charge it enough. Your lights & refer stopped working because of "low voltage". If you have a multimeter, check the battery, 12.6 + volts indicate a fully charged battery.
12.1 = 50% 11.3 = 10%
Disconnect the battery from the coach. Get it on a battery charger as soon as possible, check the water level in each cell & make sure the plates are covered, ( use distilled water ) if not, add to 1/8" below the slot of each cell. If the battery is extremely low & I suspect it is, Do not try to charge the battery with the TT convertor, it will not put enough amperage to the battery to make any difference.
Go to this web site for information regarding battery maintenance.
http://www.trojanbattery.com/tech-support/battery-maintenance/