I've built a few Outlook Add-ins now, but I have one user that is having a problem with Fabric Icons (I've also tried Google Material Icons with no luck). For that user, everything works great on OWA using IE11. But in the Outlook Desktop Client the icons are not loading. I thought the Outlook Add-in used the IE browser, so if it works in IE, it should work in the Outlook Desktop.
I know probably I should be using vorlorn.js but I haven't set it up yet (I was pulling my hair out earlier getting it to work in my local sandbox, due to Add-ins requiring HTTPS, and Vorlon not easily supporting HTTPS)
I haven't tried this yet, but if it's working in IE11 it should work on the Desktop right? Icon fonts not loading in IE11