Maybe it's to late for the answer but I had the same problem. Per default "Use Secure Tunnel connection to desktop" is enable. It determines whether View Windows Client makes a further HTTPS connection to the View Connection Server or security server host when users connect to a View desktop. If this setting is disabled, the desktop session is established directly between the client system and the View desktop virtual machine, bypassing the View Connection Server or security server host.
If this setting is enabled View Windows Clients are tunneled through the connection server. When your restart the server or services these users will lost connection to their desktops.
Zero Client don't use these Secure tunnel so you will see a blank Security gateway column.