We have been trying to get a whole bunch of servers going, and we are starting to get in to Counter-Strike... We have a number of them running but we seem to be having a few issues with CS:GO.
We have managed to get 2 running, but have issues when we try to run anymore. I know they require some sort of "key" to run properly and I have set up those keys. What I am finding is that once the configuration is done and we try and start them, despite the 2 that we have running are going well and we have had no major issues with them so far, we cannot get another 3 running with the error "Cannot connect to server" as the following screenshot shows...

Does anyone know what could be causing this error and how to fix it?