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Runbook — Outlook Keeps Asking to Sign In

Scenario

A user's Outlook keeps prompting them to sign in repeatedly, even after entering the correct password. It accepts the password but prompts again within minutes.

Steps

1. Rule Out a Service Outage

admin.microsoft.com → Health → Service health — check for active incidents affecting Exchange Online or Entra ID authentication.

2. Check if Others Are Affected

Ask colleagues or check the helpdesk queue. If multiple users are affected it is a tenant-wide issue — escalate immediately rather than troubleshooting the individual device.

3. Check Device Compliance

intune.microsoft.com → Devices → All devices → select the device → check compliance status.

A non-compliant device can trigger Conditional Access to force re-authentication on every sign in. If non-compliant, resolve the compliance issue and force a sync.

4. Check Password Expiry

entra.microsoft.com → Users → select the user → confirm the password has not expired.

If expired, reset via M365 Admin Centre and communicate the temp password securely.

5. Check Sign-In Logs for Errors

entra.microsoft.com → Users → select the user → Sign-in logs

Look for repeated failed or interrupted sign-in attempts and note any error codes. These will identify whether the issue is authentication, Conditional Access, or token related.

6. Clear the Credential Cache (Token Cache Fix)

A corrupted authentication token stored locally in Outlook is a common cause of repeated sign-in prompts.

  1. Close Outlook completely
  2. Open Credential Manager in Windows (search in Start)
  3. Click Windows Credentials
  4. Remove any entries related to Microsoft Office, Outlook, or MicrosoftOffice
  5. Restart Outlook and sign in fresh

This forces a clean authentication and resolves the loop in many cases.

7. Sign Out and Back Into Outlook

If clearing credentials does not resolve it: 1. In Outlook go to File → Office Account → Sign out 2. Close Outlook 3. Reopen Outlook and sign back in

Escalate If

  • Multiple users are affected — escalate immediately, likely a tenant-wide issue
  • Sign-in logs show a Conditional Access block — escalate to 2nd line to review the policy
  • Clearing credentials and re-signing in does not resolve the issue — escalate to 2nd line
  • Suspected Modern Authentication misconfiguration — escalate to 2nd line or IT admin

Notes

  • Clearing the Windows Credential Manager cache resolves this issue more often than expected — try it before anything more complex
  • Always check sign-in logs for error codes before escalating — they tell you exactly what is failing and save 2nd line time
  • Repeated sign-in prompts after a password change are normal for a few minutes while cached tokens expire — ask the user how long it has been happening before treating it as an issue