console logs 'The provider id_provider is not a valid one' - autodesk-forge

Question

Trying to get head around when debugging a Viewer app. Chrome console shows 'The provider id_provider is not a valid one'. Any suggestion?
If options is like this:
var options = {
env: 'AutodeskProduction',
getAccessToken: getToken }
}
function getToken () {
var response;
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
if (xhr.readyState == 4 && xhr.status == 200) {
response = JSON.parse(
xhr.responseText);
return response.access_token;
}
if forcing 2.9, 'The provider id_provider is not a valid one'.
If forcing 2.7 or 2.8, not log but the viewer doesn't show up.
If no specified version, 'Warning : no access token is provided. Use built in token : YtTb8vRA4XQfTorjm9c8eVZJTYP6'.
it stops in Autodesk360App.js
var initialItem = app.getDefaultGeometry(geometryItems);
Chrome logs 'Uncaught TypeError: app.getDefaultGeometry is not a function'
If I directly feed token:
accessToken: 'MorPwhKARIS3VGIrcd3FrZSjsnOx5'
it works beautifully in 2.7,2.8 and 2.9. But if no version, it stops in Autodesk360App.js, the same as above.
Thank you!

Answer 1

Aren't you missing the url on the http request? Maybe something line:
function getToken() {
var xmlHttp = null;
xmlHttp = new XMLHttpRequest();
xmlHttp.open("GET", '/yourTokenEndPoint', false);
xmlHttp.send(null);
var response = JSON.parse(xmlHttp.responseText);
return response.access_token;
}
For the Viewer, it must be synchronous.