The Mail and Calendar apps for Windows 10 don't support two-factor authentication. If two-factor authentication is turned on for your account, you'll need to create an app password for that account. An app password is used instead of your normal account password for apps that don't support two-factor authentication. You can sign up for a 14-day free trial, no credit card required, to sync your calendars and streamline your availability across all devices. In most cases, the only way to fix Outlook Calendar not syncing is to use a third-party Calendar Sync Tool like OneCal.

You should use the Outlook web app (explained above) to reconnect the calendars in Outlook Calendar. To manually sync a Google Calendar from Outlook, you should first remove it from Outlook. The downside of this method is that it takes up to 24 hours for events created or updated in Google Calendar to be reflected in Outlook. The second method of fixing Google Calendar not syncing with Outlook is to manually sync Google Calendar to Outlook by exporting the Google Calendar and importing it into Outlook.

Check advanced mailbox settings

Try the general troubleshooting solutions in Troubleshooting Mail and Calendar apps for Windows 10. Once you have a stable and consistent network connection, you can go ahead and follow the other advanced troubleshooting solutions. For both systems, after making changes, restart Outlook to ensure the new settings take effect.

• This section will guide you through a series of troubleshooting steps to get your calendar back on track, whether you’re using Outlook on your desktop or mobile device.
• We're on O365, most users are on the monthly enterprise channel (version 2404) with a couple early adopters on the Current channel.
• Also, be mindful of potential conflicts when multiple users edit shared calendars.
• Shared calendars in Outlook are a powerful tool for team collaboration, but they can sometimes encounter sync issues.
• Users with "Delegate" permissions are seeing all updates in real-time.
• If this doesn’t work, the only way to make it work is to use a third-party calendar automation tool like OneCal.
• The downside of this method is that it takes up to 24 hours for events created or updated in Google Calendar to be reflected in Outlook.

Troubleshooting sync issues on mobile devices

Shared calendars in Outlook are a powerful tool for team collaboration, but they can sometimes encounter sync issues. Understanding why these problems occur is the first step in resolving them. Remember, recreating your profile is often a last resort when other troubleshooting steps Reset Microsoft 365 login credentials have failed. It can be time-consuming but is sometimes necessary to resolve persistent issues. Even though Outlook is one of the most used calendar apps among individuals and businesses, offering plenty of features, sometimes it stops syncing.

Additional resources

Always ensure you have a backup of your data before making significant changes to your email configuration. Remember to restart your device after installing updates to ensure all changes take effect. If there's a feature you think is missing from the Mail and Calendar apps, or if a feature in isn't working properly, you can provide feedback directly to the Mail and Calendar team. If your password isn't the problem, you might have a certificate error.

How to fix Outlook Calendar sync issues on Android

If so, you'll see a message that says, "There is a problem with the server's security certificate. The security certificate is not from a trusted certifying authority." If you can sync your email when the firewall is turned off, you'll need to allow the Mail and Calendar apps through the firewall. Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support.

Why Is My Outlook Calendar Not Syncing?

The alternative is to wait up to 24 hours for updates from Google Calendar or Apple Calendar to be reflected in Outlook. Outlook Calendar might be working correctly, but the reason might be that there is not enough space on your Android device. Make sure you have at least more than 5GB in your device in order for new events to be stored. Connecting the Calendar again depends on the type of Calendar Provider you want to sync to Outlook. With OneCal, you don't have to worry about your Outlook Calendars not syncing.



First, ensure you have the necessary permissions to view and edit the calendar in question. Check your send/receive settings to make sure Outlook is set to update frequently enough. Verify that you’re not in offline mode and that your internet connection is stable. If you’re using a shared calendar, ask the owner to re-share it with you, as sometimes permissions can become corrupted.