UMotionControllerComponent isn't tracking

I’m using the Valve Index. Head tracking works, and the controllers are connected the headset (they appear in the Steam VR pause/settings menu) but the motion controllers aren’t tracking in-game.

I initially followed [this guide][1] which didn’t work, so instead I set it up in C++:


I don’t get any errors, but the hand won’t follow my controller, and “IsTracked” is returning false:


What am I doing wrong?