cant open outlook.com

Try these steps in order:

1. Test Outlook on the web in a private browser window.
   • Open an InPrivate/Incognito window and sign in to Microsoft 365.
   • If Outlook still does not open there, the issue is likely not the local browser cache.
2. Try signing in from the Microsoft account page first, then open Outlook from the app launcher.
   • Sign in to account.microsoft.com.
   • After sign-in, select the app launcher and open Outlook.
3. If classic Outlook on Windows also will not start, run the Outlook startup troubleshooter.
   • This applies to classic Outlook on Windows 10 or later.
   • Start the classic Outlook startup troubleshooter and follow the prompts in Get Help.
4. Reset the Outlook navigation pane in classic Outlook.
   • Close Outlook.
   • Press Windows key + R.
   • Type Outlook.exe /resetnavpane and select OK.
   • This removes customizations to the navigation pane.
5. Create a new Outlook profile in Windows if classic Outlook still fails.
   • Open Control Panel.
   • Select User Accounts > Mail > Show Profiles.
   • Select Add and create a new profile.
   • Finish account setup, then set the new profile as the one to use.
   • Risk: removing an old profile can remove associated data files if they are not backed up or stored on a server.
6. If Outlook.com still will not open on multiple computers and browsers, contact Microsoft Support.
   • This is especially relevant when the same problem happens in both Edge and Chrome or on more than one device.

References:

• Am not able to open Outlook 365 cloud - Microsoft Q&A
• I can’t start Microsoft Outlook or receive the error “Cannot start Microsoft Outlook. Cannot open the Outlook Window” | Microsoft Support
• Outlook crashes or stops responding when used with Office 365 | Microsoft Support
• Can't open outlook.com - Microsoft Q&A