In recent times, i was working with this customer where they created an Outlook add-in (Office for Apps/Office.js). They noticed that a request from Office for Apps going to ajax.aspnetcdn.com getting HTTP 502 error. During debugging (network sniffs) we noticed that issue happens that the URLs were blocked by their AV, Proxy Server settings. On fixing them, it worked as expected.
In such scenario, make sure to validate the following:
– Internet Explorer 9 or later must be installed on client computers.
– Please make sure that the affected users/computers must have external Internet access. They must be able to access the following URLs for the respective Office apps to load correctly.
– Any anti-virus solutions, firewalls or network solution is not blocking the Office.js URLs.
– Make sure that both the URL’s are accessible from IE without any problem – it’s a pre-requisite to start with.
Hope this helps.