Installing Livezilla

I am trying to install Livezilla on my site. When I get to testing the sever I get the following message.

“The server response had an invalid structure. Either the Server URL is wrong (presumably) or the server is not working properly.

Try to open the URL in your default browser. In case the URL is correct, you will see the LiveZilla serverpage.”

I have tested the URL in the browser and get the LiveZilla Serverpage. What have I got wrong?