GoToAssist, GoToMeeting, GoToWebinar, GoToMyPC, GoToRoom, and GoToTraining websites (provided by Citrix Systems) install an applet on the workstation. If authentication is enabled on the ProxySG appliance, users are prompted to enter credentials during the applet installation. If the authentication request fails, the application attempts to connect on ports other than 80. This in turn causes the firewall to reject those connections.
To resolve the issue:
Updating the Local Policy to Bypass the Web Site