Thanks, searched your history and found the map info. 
Are you using the Flight Dynamics mod for the Longitude? I’m thinking this could be related to the problem. I’m using it and per the aircraft.cfg, the bus configuration is like this:
[ELECTRICAL]
bus.1 = Connections:bus.5#Name:L_MISSION_BUS
bus.2 = Connections:bus.6#Name:R_MISSION_BUS
bus.3 = Connections:bus.5#Name:L_HOT_BATT_BUS
bus.4 = Connections:bus.6#Name:R_HOT_BATT_BUS
bus.5 = Name:L_EMER_BUS
bus.6 = Connections:bus.5#Name:R_EMER_BUS
bus.7 = Connections:bus.1#Name:L_MAIN_BUS
bus.8 = Connections:bus.2#Name:R_MAIN_BUS
…
per FSUIPC, the event when clicking the bus tie button is ELECTRICAL_BUS_TO_BUS_CONNECTION_TOGGLE with a param of 5. However, sending that event causes L ELEC to go from NORM TO EMER, and the bus tie to not change. I think that’s what you’d expect from the cfg, but I also can’t disconnect any other buses using the toggle event so it seems only param 5 is connected.
I’d really like to see the decrypted Longitude files, since it looks like we can figure this out if we look at the model xml for the bus tie button.