Outlook add-in error: When authenticating your add-in, we receive an error message and are unable to load your add-in

Question

I've been going through the process of submitting a JS based add-in to the Outlook store through Microsoft's Seller Dashboard and I'm receiving the feedback:

Requirement:

Your app or add-in must not stop responding, end unexpectedly, or contain programming errors.

Error:

We encountered an error while testing your add-in. When authenticating your add-in, we receive an error message and are unable to load your add-in.

Unfortunately there's no other information related to this request making it hard to debug or understand what is happening.

We've tested successfully on Outlook 2016 (Windows 10), Outlook 2016 (Mac OS), outlook.com (on Safari, Chrome, Firefox, and the latest version of IE) and other than a few peculiarities with how the desktop versions of Outlook handle things everything is working.

The only thing I can think of that may be triggering this is that we have a whitelist CORS approach. Currently we've whitelisted the domain our add-in is served from, but if Microsoft is bundling our add-in we'll need to whitelist the location it's eventually served from.

1. Is it likely that it's a CORS issue?
2. If so, what domains should we be whitelisting?
3. If not, how do we debug this given it works on outlook.com, Outlook 2016, and Outlook for MacOS when side loading from the same manifest xml document we're submitting through the seller dashboard?

Answer 1

Unfortunately the Office Store review team will not give many details that could be helpful. You have to provide as much testing information as possible in order for them to succeed. I had a similar loading issue at one point and they did not even bother to provide the browser type or version.

A good strategy is to output as much debugging information as you can to the browser console from your add-in's key functions. If you ask them to provide these logs in your testing notes they may be able to do that for you.

Note that the location your add-in is being served from is always your web server; Microsoft just hosts the manifest for the Office Store.

Answer 2

The error message that the screenshot is illustrating that the webpage your manifest is directing Outlook to load is not available. This means that when Microsoft is attempting to validate the add-in, the web server that the add-in is pointing to is returning a 404 HTTP Response.