How can I fix the unable to authenticate message to log n to my cell phone, for hotmail?

Follow these steps to resolve the “unable to authenticate” issue and get Hotmail working again on the phone:

1. Verify the account works elsewhere
   • On a computer or another phone where sign-in still works, go to Outlook on the web and confirm the Hotmail account and password are correct.
   • If sign-in fails there too, use the Microsoft sign-in helper to diagnose and fix account issues: Start.
2. Reset the password if needed
   • If the password may be wrong or was changed recently, reset it using the official Microsoft password reset page for personal accounts (Hotmail/Outlook).
   • After resetting, confirm that sign-in works in a browser first.
3. Update or reinstall Outlook mobile
   • On the phone, update Outlook to the latest version from the app store. Older versions can fail authentication after security changes.
   • If already updated, remove the Hotmail account from the Outlook app, then add it again using the new password.
4. Check two-step verification / MFA
   • If two-step verification is enabled on the Microsoft account, ensure at least one verification method (phone, alternate email, or Microsoft Authenticator) is working.
   • If none of the methods work or are accessible, choose I don’t have any of these at sign-in and follow the prompts to update security info or recover the account.
5. Fix verification code delivery issues
   • If codes are not arriving, check:
     • Phone can receive SMS from unknown numbers.
     • Inbox is not full and messaging app is working.
     • The phone number is a mobile number (not VOIP) and is entered correctly.
   • If blocked or seeing “Try another verification method,” avoid repeated attempts and wait up to 24 hours, then try another method (alternate email, different network) as described in the verification-code troubleshooting guidance.
6. If Outlook mobile still cannot authenticate
   • Use the sign-in helper for Microsoft accounts to detect and fix sign-in problems: Start.
   • If using a work/school account in Outlook mobile, and password reset is needed, use the work/school reset page: Reset password, or contact the school’s IT admin if self-service reset is disabled.
7. When to contact support
   • If the account is still inaccessible after using the sign-in helper and password reset, contact Microsoft Support through the official support portal and choose Microsoft account sign-in or Outlook mobile sign-in help. Depending on region, chat or callback may be available.

Once the account is confirmed working in a browser and security info is correct, re-adding the account to Outlook mobile with the latest app version typically resolves “unable to authenticate” errors.

References:

• Can't sign in to the Outlook mobile app
• Troubleshoot Microsoft verification code issues
• Common problems with two-step verification for a work or school account
• Authentication did not complete