Firstly, you'll have to make sure that the client isn't blocked in the Firewall. Locate your Firewall settings and add the application to the Exclusion list. In the Exclusion list you will see all the applications installed in your PC that are allowed to communicate with the online servers.
Also, their SIP server might be in maintenance mode, unavailable or simply discontinued. I've accessed the page of the Kall2Family and it appears that a generic IIS page is displayed instead of the actual website.
This could also indicate that the service you are trying to access is, like I said above, in maintenance mode or discontinued.