Keikikat you have a converter, not an inverter. A converter converts 120v AC to 12v DC, an inverter converts 12v DC to 120v AC. The switches you are talking about are to disconnect the batts, you have one switch for the house and one for the main that is the starting batt. You said the switch doesn't do anything. When you transfer either of these switches you should hear a big relay transfer. The relay is in the electronics box in front of the motor on the drivers side. I think you may have a blown fuse for that relay, that is also in that elect box.
Sunny South Carolina
2004 Pace Arrow 37-C WH W-22