Windows 10 October 2018 update has more errors. Microsoft will not offer the update if you have installed iCloud, and Apple will not let you install iCloud if you have already upgraded. You will also have trouble if you have F5 VPN software installed.
This information is from Microsoft's own Windows 10 Update History page, where Microsoft publicly tracks the October update.
According to Microsoft, Apple iCloud version 7.7 .0.27 has incompatibility with the latest update. You are having trouble updating or syncing shared albums after upgrading. If you try to install iCloud in the October update, you receive an error message saying "iCloud for Windows requires Windows 7, Windows 8, or Windows 10 (April 2018 update) and earlier."
Windows Update will not offer the October 2018 update if you have installed Apple iCloud. In other words, Microsoft has added an "upgrade block" to systems with iCloud installed.
If you have iCloud installed, Microsoft recommends that you do not upgrade to the October 2018 update with the downloadable update assistant tool. You must handle the iCloud behavior buggy if you bypass the block and upgrade anyway. ICloud users who clicked "Check for Updates" in early October are probably managed this error right now too. Thank you, Microsoft.
Microsoft says it works with Apple to make a future version of iCloud compliant.
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Microsoft's website also says that systems with F5 VPN clients installed "may lose network connection when the VPN service is in a shared tunnel configuration." If you have upgraded to the October 2018 update and using This software, you can force all system traffic through the tunnel to resolve this issue.
Again, Microsoft has put an "Upgrade Block" in place to prevent Windows Update from being updated with an F5 VPN installed. Microsoft is working to fix this issue.
System with Trend Micro OfficeScan or Worry-Free Business Security also has upgrade blocks at the moment, as well as systems with AMD Radeon HD2000 and HD4000 Series GPU. Mapping network devices is also broken, but system mapped network devices automatically install the update.
RELATED: Windows 10 October 2018 Update Breaks Mapped Network Drives