Yes, I can help you with your issue. As soon as you connect to vPilot on MS2020, you CANNOT change the weather or time in the game. If you do so, vPilot will erase the other planes around you on VATSIM. To fix, restart vPilot and reconnect. After I tried this the other traffic stopped disappearing. I flew in the Chicago event the other day and saw multiple planes in the sky around me at all times of the flight.
See bug discussion here: