Gimble Limits, that means it's gone as far in one direction as it can and has stuck. Hit China Hat Aft (V key) to recenter it.
To recenter your TrackIR, use whatever center button you have mapped, usually F12 I think? Or Numpad 5 to reset view then Numpad ENTER to reset zoom.
There's tons of videos online, look for users like ExcessiveHeadspace, Tigerpwrr and Revelation for some. Also the official videos from Wags.