When trying to enable the Update Manager Plugin and get this error: "There was an error connecting to VMware vCenter Update Manager
:443" , the only thing we need to to is review the logon account for the VUM Service on the Windows Server where it is installed.
Go to Services and change the Log On "This accoun" to the account with rights services for the "VMware vSphere Update Manager Service":
Stop and start the Service and go back to the Plg-in manager an enable the VUM plug-in: