That happens a lot to me too when using a single lighthouse.
Move the headset about 1 to 2 meters away from the lighthouse and turn it out around 180 degrees one way and then the other way.
Also try covering line if sight between headset and lighthouse if the other trick doesn’t work.
That usually gets it tracked.
I have no idea why and am really hoping it’ll be fixed in an upcoming firmware/PiTool version… 