I use Project Online(Microsoft Cloud service), so when I hit the REST API uri [https://<my_company>.sharepoint.com/sites/pwa/_api/ProjectData/Projects] I get the following xml error message
<?xml version="1.0" encoding="UTF-8"?><m:error xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata"><m:code>-2147024891, System.UnauthorizedAccessException</m:code><m:message xml:lang="en-US">Access denied. You do not have permission to perform this action or access this resource.</m:message></m:error>
As it is expected, when I'm already logged in, I get the xml with the list of projects. But when I hit the url from another browser with no existing logged-in session I get the above error.
Is it a matter of authentication?
Why an authentication prompt is not displayed when I hit this url with no existing logged-in session?