Cannot track face in pure Javascript from CDN

I am trying to track my face / face landmark using Javascript from CDN, but it seems not working.
I am using newest verstion of CDN (0.3.11/zappar.js).
I allow access of camera and it should work, but not working…
I tried to get face anchors information from the code, but I cannot get anything.
for (let anchor of faceTracker.visible) {

I download and test Three.js example, and it works fine.
Is there any example for pure Javascript? I can only find Usage example, but it seems not working…