How to fix calendar sync failures after changing your Microsoft 365 password

Summary

This guide helps you troubleshoot and resolve: How to fix calendar sync failures after changing your Microsoft 365 password. Follow the steps below to fix the issue.

Common Causes

Changing your Microsoft 365 password can break the link between Outlook and any external calendar services you use, such as Google Calendar. This article walks you through the quickest way to restore synchronisation, then provides detailed instructions for both Windows and macOS users, and finishes with extra troubleshooting tips.

Quick Fix Steps

1. Close Outlook completely.
2. Open Windows Credential Manager (or Keychain Access on macOS) and delete entries that start with MicrosoftOffice16_Data: or MicrosoftOffice15_Data:.
3. Restart Outlook; you will be prompted to enter your new Microsoft 365 password. Type it in and select Remember my credentials.
4. Open your Google Calendar sync tool (e.g., Outlook Google Calendar Sync) and re‑authenticate using your Google account credentials.
5. Wait a few minutes for the first sync cycle, then verify that events appear in both calendars.

Detailed Instructions

1. Update Outlook (Windows)

1. Press Ctrl + Shift + Esc to open Task Manager and end any Outlook.exe processes.
2. Press Win + R, type control keymgr.dll and press Enter to launch Credential Manager.
3. Click Windows Credentials, locate entries that start with MicrosoftOffice16_Data: or MicrosoftOffice15_Data:, and choose Remove.
4. Open Outlook again. When prompted, enter your new Microsoft 365 password and tick Remember my credentials.
5. Navigate to File → Account Settings → Account Settings, select your Microsoft 365 account and click Repair to force re‑authentication.

2. Update Outlook (macOS)

1. Quit Outlook via Outlook → Quit Outlook or Cmd + Q.
2. Open Keychain Access from Applications → Utilities.
3. Search for “MicrosoftOffice” and delete any matching items.
4. Re‑open Outlook; you will see a sign‑in window. Enter your new password and, if asked, approve any multi‑factor authentication prompt.

3. Re‑authenticate Google Calendar Sync Tool

1. Open your sync application (e.g., Outlook Google Calendar Sync).
2. In the Settings tab, click the Authenticate button next to the Google account.
3. When the Google sign‑in page appears, log in with your Google account credentials, not your Microsoft 365 credentials.
4. After successful authentication, click Save Settings and then Start Sync.
5. Check the sync log for any errors; a green “Sync completed” message means the connection is restored.

4. Verify Calendar Sync

• In Outlook, open the Calendar view and create a test event titled “Sync Test”. Set the time for a few minutes ahead.
• Switch to Google Calendar (web or app) and confirm the event appears.
• If the event is missing, run another manual sync from the sync tool and re‑check.

Troubleshooting

Common Issues

• Sync stops after the first run – often caused by outdated cached credentials. Repeat the Credential Manager or Keychain steps.
• Authentication errors – ensure your Microsoft 365 account is not locked and that any required multi‑factor authentication (MFA) is completed.
• Events disappear – check that the sync direction is set correctly (e.g., Outlook → Google, Google → Outlook, or bidirectional).
• Modern authentication / OAuth2 failures – if your organisation uses MFA, your sync tool may require an app password instead of your standard Microsoft 365 password. Generate an app password in your Microsoft 365 account security settings and use it when re‑authenticating the sync tool.

Advanced Checks

1. Open a web browser and sign in to Microsoft 365 portal to confirm your new password works.
2. Visit Google Workspace Status Dashboard to verify there are no service outages.
3. In Windows, run netsh winsock reset from an elevated Command Prompt and reboot – this can resolve hidden network stack issues.
4. On macOS, if Outlook continues to fail, contact your IT administrator before attempting any manual cache deletion, as incorrect folder removal can cause data loss.

When to Seek Further Help

If you have followed all steps and the calendars still do not sync, please Open a Ticket and include the following details:

• Operating system and version (e.g., Windows 10 22H2, macOS 14.2)
• Outlook version (File → Office Account → About Outlook)
• Name and version of the Google sync tool you are using
• Any error messages from the sync log

Still Having Issues?