New Input XR System Vive Touchpad

Hi,

I'm trying to get the vives' controller's touchpad data:
device.TryGetFeatureValue(CommonUsages.primary2DAxis, out touchPos);

But touchPos is always zero, even if I try touch both controllers touchpad. Is that what I should be using to get that "circle touchpad X,Y position"?

What am I missing?

Thanks!
Jeff.