Hi, I'm John! I will help you with this.
To help narrow down the issue:
- Are you getting any specific error message? If so please share, or tell what happened.
- Have there been any recent events, such as a hacking incident or password change?
- Is this happening on all devices, or just on certain devices? Are you using Outlook Web, Outlook for Windows, or the Outlook mobile app?
Click "Add comment" to let me know.