Hi, @jc296 

You are correct, if you tried to upgrade to Windows Server 2019 with Connection Server installed on Windows Server 2012, VMware would not have approved that action because it would be an in-place upgrade!

Not only Connection Server, but also for Horizon Agent, if you want to apply Windows Feature Update, you should uninstall Horizon Agent , VMware Tools, and then perform Windows Update. Windows Update should be performed after uninstalling the Horizon Agent and VMware Tools.