u/Efficient-Ant-7581

have been flying the PMDG777-200ER
But whenever I start the aircraft on my gate in cold and dark state, I am not able to Change Squawk code it just stays at 1234 but when I start the craft from the runway, then it works
Due to this, I am not able to play on that VatSim. Does anyone know why that happens and how to fix?
Thankyou.