In case anyone else has this issue, try re-executing/activating a flight plan in the FMS system, maybe even changing it slightly and back again. When I do this in the CJ4, the sim treats it as if I’m wanting to file a new flight plan and I get a new IFR request option in the ATC window. I.e. If given a specific transition for an approach, I’ll modify the FMS route to add it, then I could radio that in as an entirely new plan as far as ATC is concerned (only I don’t do this since I’m still using the original route).