Autodesk forge, load graphics display black

load the model, the container turns black.
at first thought it was my program"s problem. But try it with the code of the example, too.
is there something wrong with the server?
the following is the source code of the example. It used to be possible. Not anymore.

< html >
< head >

<meta charset="UTF-8">
<script src="https://developer.api.autodesk.com/viewingservice/v1/viewers/three.min.css"></script>
<link rel="stylesheet" href="https://developer.api.autodesk.com/viewingservice/v1/viewers/style.min.css" />
<script src="https://developer.api.autodesk.com/viewingservice/v1/viewers/viewer3D.min.js"></script>

< / head >
< body onload= "initialize ()" >
< div id= "viewer" style= "position:absolute; width:90%; height:90%;" > < / div >
< script >

function authMe () { return ("eyJhbGciOiJIUzI1NiIsImtpZCI6Imp3dF9zeW1tZXRyaWNfa2V5In0.eyJjbGllbnRfaWQiOiJIalFGcGpyU0JIM3EyMkJETVZGUGdZYjdzVkFZRmFiSiIsImV4cCI6MTUyMDI1OTMzNywic2NvcGUiOlsiZGF0YTpyZWFkIiwiZGF0YTp3cml0ZSIsImJ1Y2tldDpjcmVhdGUiLCJidWNrZXQ6cmVhZCJdLCJhdWQiOiJodHRwczovL2F1dG9kZXNrLmNvbS9hdWQvand0ZXhwNjAiLCJqdGkiOiJhc294RjJQU3Q3VGVORkh1TXVDWWV3b052cnFpRWU5VjREbkxCZUhFeVZDcnJSWnZ3V1FwbW83M0tDYzM1NzBEIn0.0mkXxMhJ-JRYjD7qjLcM3IOinShEV-kqLJMzQhvDVzA") ; }

function initialize () {
    var options ={
        "document" : "urn:dXJuOmFkc2sub2JqZWN0czpvcy5vYmplY3Q6Zm9yZ2UtY3NoYXJwLXNhbXBsZS1hcHAtaGpxZnBqcnNiaDNxMjJiZG12ZnBneWI3c3ZheWZhYmovbXktZWxlcGhhbnQub2Jq",
        "env": "AutodeskProduction",
        "getAccessToken": authMe
    } ;
    var viewerElement =document.getElementById ("viewer") ;
    //var viewer =new Autodesk.Viewing.Viewer3D (viewerElement, {}) ; / No toolbar
    var viewer =new Autodesk.Viewing.Private.GuiViewer3D (viewerElement, {}) ; // With toolbar
    Autodesk.Viewing.Initializer (options, function () {
        viewer.initialize () ;
        loadDocument (viewer, options.document) ;
    }) ;
}
function loadDocument (viewer, documentId) {
    // Find the first 3d geometry and load that.
    Autodesk.Viewing.Document.load (
        documentId,
        function (doc) { // onLoadCallback
            var geometryItems =[] ;
            geometryItems =Autodesk.Viewing.Document.getSubItemsWithProperties (
                doc.getRootItem (),
                { "type" : "geometry", "role" : "3d" },
                true
            ) ;
            if ( geometryItems.length <= 0 ) {
                geometryItems =Autodesk.Viewing.Document.getSubItemsWithProperties (
                    doc.getRootItem (),
                    { "type": "geometry", "role": "2d" },
                    true
                ) ;
            }
            if ( geometryItems.length > 0 )
                viewer.load (
                    doc.getViewablePath (geometryItems [0])//,
                    //null, null, null,
                    //doc.acmSessionId /*session for DM*/
                ) ;
        },
        function (errorMsg) { // onErrorCallback
            alert("Load Error: " + errorMsg) ;
        }//,
        //{
        //    "oauth2AccessToken": authMe (),
        //    "x-ads-acm-namespace": "WIPDM",
        //    "x-ads-acm-check-groups": "true",
        //}
    ) ;
}

< / script >
< / body >
< / html >