by Ute Seward
on December 25, 2025

If you’re not an admin, ask your IT department to check this for you.
Turn off Windows Defender Security Center
Why do I keep getting a sync error on my calendar?
Try the general troubleshooting solutions in Troubleshooting Mail and Calendar apps for Windows 10. All of my users use Outlook on the Web in Chrome.for one day -using incognito mode solved the mail won’t send message. After confirming synchronization is not working, follow the solutions discussed below to troubleshoot the issue. Remember, changes to these settings might require you to restart Outlook or even your computer to take effect. Always ensure you have a backup of your data before making significant changes to your email configuration.
Check the connectivity to your email server
If you’re using an IMAP or POP account, some of these options may not be available, and you might need to check your account-specific sync settings. Calendar syncing plays a pivotal role in maintaining an organized and efficient schedule. Whether you’re managing personal appointments or coordinating team meetings, a synchronized calendar ensures that everyone is on the same page, literally and
Help from FixTechGuide figuratively. Outlook will load a new fresh profile and synchronize all mail items from the mailbox server.

Check your security software
If you haven't installed alternative security software, you should temporarily turn off Windows Defender Security Center. My user list of who has editor permissions to the known 15+ accounts is not the entire company. Health center even is reporting a syncing issue - though clearly the issue is much larger than just syncing. Remember, creating a service ticket usually requires admin privileges.
How to Fix Shared Calendar not Syncing with Outlook?
If you’re not an admin, you’ll need to contact your IT department to create a ticket on your behalf. Remember to restart your device after installing updates to ensure all changes take effect. We're on O365, most users are on the monthly enterprise channel (version 2404) with a couple early adopters on the Current channel. Two-factor authentication helps protect your account by making it more difficult for someone else to sign in. It verifies your identity using your password and a contact method (also known as security info). While not directly related another calendar issue is still on the tracker.
By repairing or reinstalling MS Office, you can fix any issue with the Outlook program files that might be damaged, leading to the synchronization issues in the Outlook program.Try the general troubleshooting solutions in Troubleshooting Mail and Calendar apps for Windows 10.Remember, changes to these settings might require you to restart Outlook or even your computer to take effect.
If the shared calendar is syncing, then find and remove the faulty add-in to fix the issue permanently. By leveraging these features, teams can significantly reduce the occurrence of sync issues and improve overall calendar management efficiency. When your Outlook calendar isn’t syncing properly, it can throw your entire schedule into disarray.