If you create a flight plan in the EFB, or import it from NAVIGRAPH into the EFB, there’s an issue SENDING that to the ATC/Avionics in the Citation X, once the jet is active in an airport. It doesn’t send. You have to load or create the flight plan in the EFB and send it before going to the airport in the World Map. Then it works. Unless someone else has had success with this after starting up the jet. I have not.
I think this is listed as a known issue:
https://devsupport.flightsimulator.com/t/msfs-2020-planes-avionics-flight-plan-issues/14103/19
Regards,
Tim