https://wccftech.com/apple-fixes-icloud-windows-10-1809/

Microsoft had put an upgrade block on Windows 10 October 2018 Update machines trying to install iCloud for Windows (version 7.7.0.27). Those who were already running this version were blocked from receiving the latest version of Windows 10.

Apple has today issued iCloud for Windows version 7.8.1 potentially to address compatibility issues with Windows 10 version 1809. The company has also removed the restriction that iCloud is only compatible with Windows 7 through Windows 10 April 2018 Update. The support page now simply reads Windows 7 or later: