Show AI traffic is ticked to. What could be a filter in EFB? vPilot is set to Do Not Display Aircraft beyond 100NM and maximum aircraft to display 999.
As said, if I'm on the ground I can see planes taxing but in the air nothing, also the offline mode showing planes at gates is working. I even moved the displayunit to the FSX computer to be sure it's not something from the network.
This could of course be a vPilot issue, so if there is a way to rule out the EFB that would be nice too.