Why are all my agent system tray icons grayed out

Why are all my agent system tray icons grayed out

All my agent icons are grayed out. I right clicked on a grayed out agent and ran the troubleshooter, and it says everything is fine.  When I try to remote control an agent, I get an error saying "Unable to establish connection with agent".
      I can run a scan of the workstations and the scan succeeds, so I know the server is talking to the workstation.
      I checked and port 8443 is open on the server, but not on the workstations. Does it need to be open on the workstations too?  
Any idea why the I can't remote control my workstations?

Thank you