Can't Log into Outlook classic on desktop

Classic Outlook is likely still using cached credentials and an outdated authentication method. To resolve this, clear the old credentials, re‑authenticate, and, if needed, use the classic Outlook authentication troubleshooter.

Follow these steps:

1. Remove old cached credentials in Windows
   1. Open Control Panel → User Accounts → Credential Manager → Windows Credentials.
   2. Remove any entries related to Outlook, Office, Microsoft 365, or the affected email account.
   3. Close Credential Manager.
2. Make sure the correct (new) password is used in Outlook
   • If this is a classic Outlook profile that previously worked and now keeps asking for a password, it often means:
     • The password was changed with the email provider and not updated in Outlook, or
     • The password expired and must be updated.
   • After clearing credentials, start Outlook again and when prompted, enter the new password and complete any sign‑in prompts.
   • If using an IMAP provider that requires an app password (for example, if you see a message like “Please create an app password for Outlook on your email provider's site”), generate that app password with the provider and use it in Outlook instead of the regular password.
3. If Outlook is not prompting correctly or keeps looping
   • For IMAP accounts in classic Outlook, ensure Require logon using Secure Password Authentication (SPA) is unchecked on the account’s IMAP settings page.
   • If Outlook never properly asks for a password, recreate the mail profile via Control Panel → Mail → Email Accounts → New, then add the account again and enter the new password when prompted.
4. Run the classic Outlook authentication troubleshooter
   • Use the Classic Outlook authentication check troubleshooter to fix password/auth issues:
     1. Open the Get Help app in Windows.
     2. In the search box, type Outlook password problem.
     3. Run the troubleshooter and follow the steps it provides.
5. If Microsoft Authenticator is still registered but not showing prompts
   • Sign-in may be waiting for a second factor that never arrives. After clearing credentials and recreating the profile, Outlook should re‑trigger the sign‑in flow so the correct method (password + current 2FA method, or app password) can be used.
   • If sign‑in still fails, use a browser to sign into the account, review security info, and ensure the correct phone/email/Authenticator methods are active, then repeat the Outlook sign‑in.

References:

• Troubleshoot Outlook email setup
• I can't send or receive messages in Outlook
• Classic Outlook troubleshooters
• Do you know how to fix the issue where Outlook keeps prompting for a password even though credentials are saved - Microsoft Q&A
• Outlook ask for credentials every minute - Microsoft Q&A