as of recently, Simbrief flight plans containing SIDs and STARs can no longer be imported into the X-Plane 12 Hot Start Challenger.
Please refer to the statement here: Simbrief FPLN REJECTED - Technical Support - X-Pilot
It appears that there:
" They (Simbrief) are encoding a fictitious SID transition (using the SIDTRANS line) that doesn’t actually exist in the database. In the case of GZO3D (a SID from airport LMML), they’re encoding the terminating waypoint as if it was a named enroute transition (GZO), which it is not (GZO3D contains no enroute transitions). The file with the SID & STAR would load just fine if they simply left that one line out. The official Laminar .FMS file format specification makes this clear: If the departure has no transitions, the SIDTRANS line can be omitted."
This is just one example. There are more departures in Europe which do not feature any transitions, and hence should not have the terminating waypoint encoded as a transition.
Please have a look into this.