I had figured out the solution for this but then I forgot where fuel panel control actually was. 😅
Now as I am in the middle of the flight at the moment, I came across it in the maintenance tab on the OIS. If I am not wrong, its the Fuel Panel button here that will close the fuel panel. I am mid-cruise at the moment and it wont let me close the fuel panel any more because I get a message saying "you cannot open the fuel panel mid-air", even though the panel is already open. Let me know if this works because I cannot test it at the moment and I am doing a medium haul flight with the fuel panel open 😂
@iniBuilds Perhaps a small bug that slipped under the radar.