Can't use the Platform in Standalone Mode, and Users.GetLoggedInUser() does not work.

[wappaboyVR]

I want to get Data of logged in Oculus user, so I went to this page documentation/unity/ps-setup/ and tried to activate "Use Standalone Platform", but that checkbox was disabled.
Also the following script does not work on the first line. Users.GetLoggedInUser() seems to be NULL.
How do I get it to work in Standalone mode?

void Start()
{
    Users.GetLoggedInUser().OnComplete((Message<User> uMsg) =>
    {
        if (uMsg.IsError)
        {
            Debug.Log("Platform: GetLoggedInUser() failed. Reason: " + uMsg.GetError().Message );
            return;
        }
        else
        {
            User _localUser;
            _localUser = uMsg.Data;
            Debug.Log(_localUser.DisplayName);
        }
    });
}

[Using game engine and Oculus SDK]
Unity 2019.4.18f1 (LTS), Oculus SDK 1.55.1

[wappaboyVR]

Here's a screenshot of the OculusPlatformSettings.
"Use Standalone Platform" is disabled.