Issue: When a user attempts to sign into an Office 2016 application on a system running Windows 10, the sign-in window either blank or shows a "Signing In" message with no progress:
Cause: Because of the introduction of Web Account Manager in newer builds of Office and Windows, non-secure endpoint (non-HTTPS) traffic is blocked in authentication workflows. Please read this Microsoft Bulletin for further details.
Resolution: Make sure that all IWA servers are configured with SSL certificates. Please refer to our Install and configure the Okta IWA Web App for Desktop SSO guide for additional guidance on enabling SSL for IWA. (Section entitled: "Configure SSL")