iCloud Control Panel Windows Sync Issues

To solve sync issues at Windows / Outlook side

1. Run the iCloud Control Panel on your PC
2. Untick the box next to Mail, Contacts, Calendars, and Tasks
3. Apply the changes by accepting the prompt message
4. Tick back the box next to Mail, Contacts, Calendars...
   and run Outlook on your PC to see whether the contacts and calendars are now re-syncing correctly.

If this doesn't work

1. Close Outlook
2. Sign out and back in to iCloud Control Panel
   Signing out of iCloud Control Panel and signing back in will reconfigure Outlook for use with your iCloud account.
   Important: Any attachments you added to calendar events from Outlook will be lost.
   All of your other data is stored in iCloud, and will be downloaded to your PC when you sign back in with iCloud Control Panel.
3. In Windows 8.1: Go to the Start screen, click the down arrow  in the lower left corner, then click the iCloud app.
   In Windows 8: Go to the Start screen, then click the iCloud tile.
   In Windows 7: Choose Start menu > All Programs > iCloud folder > iCloud
4. Click Sign out.
5. When prompted to save or delete your data, click Delete.
6. If prompted to view your iCloud Photos folder, click Cancel.
7. Sign back in to iCloud Control Panel.
8. Select the features you want to enable including Mail, Contacts, Calendars and Tasks.
9. Click Apply, then close the iCloud Control Panel.
10. Open Outlook.