First of all, welcome to the Forums. We're glad to have you with us.
As to your electrical problem. In an Airstream the are component that run only on 110 volt AC power. These are your air conditioner/heat pump, microwave, refrigerator (usually), television, and the household type outlets. The other electrics are all powered by 12 volt
DC. This is true even while on shore power. the shore power powers the converter which turns 110v AC into 12v
DC. The interior lights, furnace fan, Fantastic Fan, etc. all run on 12v
The problem you decribe may have been caused by the master switch remaining in the store position. This switch should switch out of store position when the system is hooked up to shore power. Try this switch when not hooked to shore power. The red indicator light should come on, and your 12 volt
stuff should work. This is all assuming that the batteries are good.