I set up the flight plan in SimBrief and use the prefile for VATSIM yet when I do that and open flightplan on vpilot it doesn’t work and sends me to the website instead of the pop up window.
Not sure what you are trying to do? Fill out the flight plan form on my.vatsim.net, press the file flight plan button, connect to the network, and if you have done everything correctly the controllers will see your flight plan.
You cannot file a flight plan in vpilot any more.
When you file via Sim Brief, then go to Prefile, prifile to vatsim, then scroll down to the bottom og the shown flightplan and pressq the green button File Flightplan and everthing is in order