I had this problem. I fixed it using this fix in the x-plane manual under troubleshooting:
If you are running the latest version of the simulator and still have problems, another good place to look is at the preferences. Move the preferences folder (found in the Output folder) to the desktop, then restart X‑Plane and default preferences will be restored. If the default preferences do not fix your problem, you can simply replace them with the folder you moved to the desktop and restore your personalized settings.