Microsoft FSX steam edition install steps.
After installing Microsoft FSX Steam edition to your C: drive
Head to C:\Program Files (x86)\Steam\steamapps\common\FSX\SDK\Core Utilities Kit\SimConnect SDK\LegacyInterfaces
In that folder should be three Simconnect.msi files, install all three!
Head tracking in FSX should now be working using either the Simconnect or FreeTrack protocol.
If you are still experiencing issues then please contact support.