There is an issue with Office 365 Apps not working with DUO Security MFA? This is particularly problematic on Windows 10 Mobile. The second authentication page presented by DUO Security is not rendered. Microsoft staff believe DUO Security is not up to date on Modern Authentication. Yet, the same expected rendering works with some Office 365 apps but not all of them. The issue is present in Delve, Skype for Business, and PowerApps. However, Teams, SharePoint, and Yammer work fine with DUO Security..