If you have the Intellitec battery disconnect switch it has two fuses on it. You would need to check those fuses and the connectors to them.
You could manually flip the switch by putting 12 volts to the proper pin with a jumper wire to see if the switch is at fault or the circuitry. If you can flip it with a jumper. It shouldn’t take too much to find the circuitry problem.
A schematic is available on the Intellitec battery switch page with troubleshooting instructions.