Cannot enable Q_GUIDED_MODE parameter

Hi everyone, i need help with my problem… First i start my simulation by running sim_vehicle.py on the terminal and everything is working fine, but when i change 1 parameter which is Q_GUIDED_MODE to 1, then suddenly the simulation is not working anymore. It shows “Attempting to reconnect” and “[errno 111] Connection refused sleeping”…

Any idea why it happen? Thank you