Using classic Outlook for Windows in business environments
Common issue, why MS hasnt fixed this is a head scratcher. Here are a few things to try that have worked for me. (1) get into "Task Manager" and End all tasks with "Outlook" in their name. Now try opening Outlook. (2) Reset Outlook. But you'll have to re-enter all your email account info. (3) Sometimes a simple reboot does the trick. Warning, eventually the problem comes back. Frustrating issue.