Office add-in sometimes won't load and instead opens webpage

Question

Ever seen an issue with an Office add-in where the it sometimes won't load and instead opens itself as a blank page in a browser? This sometimes happens to one of my clients who installed my Outlook add-in. When they open it, it immediately pops open a webpage in their browser that first redirects to a Zscaler link, and then directs to the add-in link, which is https://office-eu.testingcenter.net/ReportPhishing.html?killphish_instance=db3791d4-ff2e-45b5-8efe-b767d4e85004&et=#. I'm not sure if the issue is caused by Zscaler itself, or Microsoft, or with the add-in.

Most of the time, the add-in loads fine for this customer. But maybe 2% of the time, this odd behavior occurs. I've attached a screenshot of what the add-in normally looks like when opened as well as a screenshot of what it looks like when it opens the page in a browser. I'm not seeing any errors in the JS console or on my backend related to this. This issue is occurring on OWA, Outlook desktop, and the new Outlook (PWA).

Answer 1

The client had to add the add-in URL to their Zscaler allowlist.