Same thing happened in my install. The only thing I can think of that the model is a port and that ports no longer work in the latest versions of MSFS.
I'm afraid that this will take someone with greater skills than mine to make her work.
Priller
Have you mapped your throttle to the Throttle1 axis or Throttle?
I use Throttle1, which is needed for Hawk/104/DC's Jets and presumably for the D21 as it works fine for me
You need to delete the Throttle mapping too, just have Throttle1.