Microsoft Flight Simulator X is more involved than games that only need a single LookPilot protocol. External head pose goes through SimConnect, which opentrack drives—not a SimConnect option inside LookPilot.
LookPilot: set Protocol to opentrack (UDP into opentrack).
Opentrack and SimConnect: install opentrack from the opentrack releases page, then follow opentrack’s SimConnect protocol documentation for the SimConnect client (SimConnect.msi), choosing Microsoft FSX SimConnect as output, picking the right manifest, starting opentrack, and troubleshooting.
With LookPilot: use OpenTrack setup with LookPilot (LookPilot Protocol opentrack, opentrack Tracker UDP over network). After SimConnect is configured in opentrack, click Start tracking in LookPilot, Start in opentrack, then launch FSX. Fully quit and restart FSX once after the first-time setup if the sim does not react.
A similar overall workflow is described in Beam Eye Tracker’s FSX: Steam Edition guide.
Usually no separate in-game “enable TrackIR” step is required once opentrack’s SimConnect output is working. If the camera still does not move, use the Troubleshooting section in opentrack’s SimConnect protocol documentation.