We have several users who are experiencing the disappearing password/credentials window. The system needs the password to be entered. Click on the "Need Password" option (ribbon or task bar) and Outlook very briefly launches a pop-up window which would normally allow the credentials input, but it disappears. Can't alt+tab to it. It's not there. We're current Office365 Outlook 2016 users, updates current, dual authentication active for the company. I would think this would be a credentials manager issue. System restart seems to fix it. But because it's happening across the company, I'm wondering if there's a known issue out there.