Web addin fails in Outlook for Windows with: "Office.js has not fully loaded"

Question

We created an Outlook web addin and it is working fine in OWA and in Outlook for Mac. On Outlook for Windows however, the addin only shows a blank page.

When attaching a debugger, we get the JavaScript error

Office.js has not fully loaded. Your app must call "Office.onReady() as part of it's loading sequence (or set the "Office.initialize" function").

This is Outlook 2016.

We do call Office.onReady and we also tried inserting an empty body for Office.initialize.

I have a feeling that IE is not happy about the JavaScript we are using (Knockout.js perhaps?). We also tried adding <meta http-equiv="X-UA-Compatible" content="IE=edge"> but all to no avail.

How can I figure out what is going wrong?

Answer 1

I was facing the similar issue, so I tried to run the add-in on IE11 (to get the actual reason behind the issue), and found the issue there, and by resolving that, it worked on Outlook desktop client too.

Thanks @Outlook Add-ins Team for the important comment.