Last year during the roll out of the October 2018 Update for Windows 10, Microsoft encountered compatibility issues with the Apple iCloud app, version 22.214.171.124 to be exact. Instead of leaving it to Apple to make corrections, Microsoft simply blocked the iCloud users from the October 2018 Update.
By November the issue had been taken care of from both ends, iCloud and Windows and Microsoft removed the update block in question. This meant that users could update to the latest version of iCloud which would solve the compatibility issues and hence update Windows 10. But it meant that users had to manually update Windows in order to get the Windows 10 version 1809. Since then, only a small proportion of iCloud users are running the version 1809 because let’s face it, no one manually updates Windows on their PC.
On February 1, 2019, Microsoft published a support document that the devices blocked from the Windows update last year because of iCloud will automatically be offered Windows 10 version 1809.
This update will be sent to all the users which were blocked earlier and it will show up on your device as any other Windows updates do by mid-February.
If you are an iCoud user and believe that your device was blocked from this update, you can update to the latest version of iCloud from here and then go to Windows Update Settings on your PC to update to the latest version of Windows 10.