Users have reportedly discovered that iCloud stops working on laptops updated to the latest version of Windows (1809). This prevents syncing or uploading to the service. New installs of iCloud may also fail due to a lack of compatibility. Microsoft has announced a collaboration with Apple to fix the problem.
https://www.notebookcheck.net/iCloud-found-not-to-work-with-Windows-October-Update.364256.0.html