new Battery ? fully charged ? recently changed ?
no interior lights ? water pump quit working ?
everything worked before this ?
missing wire or wrong connection is the most likely possibility
or
do you mean, the 120v items and duplex receptacles ?
those don't work on 12v battery power
those work from shore power, or generator
or from an INVERTER attached to the batteries
an inverter is a device that uses battery power to make 120v power
and normally use to run the TV etc..
NOT the air conditioning or the MW, big power items need the generator, unless you invest big $$ in batteries and solar, and then you still need to recharge the batteries using the generator