Your problem is likely you are running the sim into a "Compatibility" mode, like XP under Windows 7/8 or Windows 7/8 under Windows 10, which is wrong, since by default the sim installs without any Compatibility settings, and that's now it should work.
Be sure you uncheck any Compatibility settings for the Prepar3d.exe file.
Also, be sure you user account is not of the limited kind.