Invalid OAuth2 Token when using GetUserProof API to generate nonce for non-developer user account

Hi there, I've encountered an issue where a non-developer user account is getting Invalid OAuth2 Token when trying to call the Platform.Users.GetUserProof API to generate a nonce on the client application (local development build).

I wonder if the user has to be part of our oculus developer organization in order to consume this API? I don't see any relevant doc explaining it or similar issues from other developers yet. But I've attached the stacktrace for your reference. Note: The GetUserProof API would work fine with developer account under our scoped organization. 

Thanks for your help in advance! 🙂