Cannot create OVRSpaceUser for sharing Spatial Anchor

As per the Shared Spatial Anchors Sample (https://github.com/oculus-samples/Unity-SharedSpatialAnchors) I need to create a list of OVRSpaceUsers which to share the OVRSpatialAnchor with. But when I create an OVRSpaceUser using the Oculus ID from the logged in user, the OVRSpaceUser turns out invalid and the id defaults to 0.

What am I doing wrong?