Using Classic Outlook on Windows for personal email, calendar, and contact management
Hi there, this is Marc. Thanks for reaching out to the community.
This can be caused by a number of things. I need to get a clear picture of what's happening on your end before we go any further.
Are you using the Outlook desktop application that's installed on your computer, or are you trying to access your email through a web browser like Chrome or Edge?
If it's the desktop app, do you get any specific error messages when it fails to open?
In the meantime try this basic troubleshooting, Go to https://outlook.com in your browser and try signing in there first. If that works, the issue is with your Outlook app, not your account. If the website login fails too, reset your password at https://account.live.com/password/reset.
For the Outlook app, close it completely through Task Manager (look for any Outlook processes and end them), then try starting Outlook in safe mode by pressing Windows+R, typing "outlook /safe" and hitting Enter.
If safe mode works, you have a corrupted add-in or profile. Go to Control Panel > Mail > Show Profiles and create a new profile.
Best regards,