May want to take a peek at the manual.
Flight Plan Synchronization Between the Game and FMS
- You can still “file” your flight plan to ATC by entering it in the world map of MSFS and it will remain visible to ATC/VFR.
- To load the plan into the FMS you can either enter it manually or use the FPLN RECALL (GAME/SB) option in IDX → PAGE2 → ROUTE MENU
- Due to the increased accuracy and capabilities of the FMC managed flight plan, you may find that the sync to the game does not always work as expected or does not reflect the FMC flight plan.