Question : Web Interface 5.3 PNAgent Site - Citrix Online Plug-in could not contact the server entered.

When trying to connect to a newly created site, we get the error "Citrix online plug-in could not contact the server entered.  This may be because the server is down, there is an error in the configuration file from the server, or the details entered are incorrect".  In the event log we will see Event ID 40001 - Site path: C:\inetpub\wwwroot\Citrix\PNAgent.  An error occurred while enumerating a user's resources. An unrecognized XML message was received from a user device. [Unique Log ID: 803545b].  

We are running XenApp 6 with WI 5.3 and are using the latest online app.  There is a web interface site working correctly.  XML port 8080.  Connections attempts from the server itself fail in the same way.  We have the Trust XML setting enabled in the Computer Policy.  We have tried multiple times to delete and reinstall the site with no luck.  The OS firewall is disabled.  If there is anything else I can provide please let me know.

Answer : Web Interface 5.3 PNAgent Site - Citrix Online Plug-in could not contact the server entered.

And are you connecting to the WI on http (80) or https (443)? If you are connecting on 443, are you able to install SG too? I would recommend it if you can.

In the WI setup, try configuring the server within the Server Farm settings, make sure the XML Service Port is set to 8080, and HTTP transport type. As before, try using the IP address of the Citrix servers instead of the FQDN.

I've written an article on installing WI and SG on my website (apologies in advance if external linking isn't allowed), maybe there is something to help you there - http://www.leeosborne.co.uk/wp/how-to-install-and-configure-citrix-web-interface-5-3-and-secure-gateway-3-2-part-1/