Published 2024-07-15 by TechNet New England
Calendar sync issues in Outlook are usually caused by account configuration, cached data, or a conflict between devices. ## Check the Basics 1. **Is the calendar visible?** In Outlook, look at the left sidebar under Calendars. Make sure the correct calendar is checked. Shared calendars or room calendars may be unchecked. 2. **Are you looking at the right date range?** Click "Today" to make sure you are viewing the current date. 3. **Does the meeting show in webmail?** Go to outlook.office.com and check the calendar there. If it shows online but not in the desktop app, the issue is with the app. ## Fix 1: Toggle Calendar Sync On mobile devices (iPhone, Android): 1. Go to phone Settings > Accounts (or Mail/Calendar accounts). 2. Select your email account. 3. Toggle **Calendars** off, wait 10 seconds, toggle it back on. ## Fix 2: Remove and Re-add the Account If calendar events are missing on one device: 1. Remove the email account from that device. 2. Add it back. 3. Wait for the calendar to re-sync. This forces a fresh download of all calendar data from the server. ## Fix 3: Clear the Outlook Cache (Windows) 1. Close Outlook. 2. Press **Win + R**, type `%localappdata%\Microsoft\Outlook`, press Enter. 3. Delete the .ost file for your account (it will be recreated when Outlook reopens). 4. Reopen Outlook and let it re-sync. Warning: This re-downloads all email and calendar data. It may take a while for large mailboxes. ## Fix 4: Check Calendar Permissions (Shared Calendars) If a shared calendar is not showing: 1. Ask the calendar owner to verify sharing permissions. 2. In Outlook, try adding the shared calendar again: File > Open and Export > Open Shared Calendar. 3. For Microsoft 365, shared calendar permissions are managed through the admin center or by the calendar owner. ## Fix 5: Check Outlook Add-ins Some add-ins can interfere with calendar sync. 1. Open Outlook in Safe Mode (Win + R, type `outlook.exe /safe`). 2. If the calendar syncs in Safe Mode, disable add-ins one by one to find the culprit. ## Mobile Sync Issues **iPhone:** Make sure the Outlook app or the built-in Calendar app is configured with the correct account. If using the built-in Calendar, go to Settings > Calendar > Accounts and verify sync is enabled. **Android:** If using the Outlook app, go to Settings within the app, select the account, and verify calendar sync is on. ## When to Contact IT If calendar sync fails across all devices after trying the above, the issue may be server-side. Your IT provider can check Exchange Online configuration, calendar processing rules, and account health.