Problem to connect with our server can depend on different things. 

In some cases, our server becomes temporary overloaded. Then just wait for a couple of minutes and try again.

You could have a firewall installed that only let traffic through to sites previously approved by a network technician. There could be that all your traffic is going through a proxy server and that you will have to configure the settings for the proxy server in CNCSimulator (you will get a chance to do that if the startup fails). It can also happen if you have an unreliable connection to Internet, like a weak Wi-Fi signal for example. In any case, if you can’t solve the problem yourself, you will need to contact your ISP (Internet Service Provider) or if you are at an institution or a company, the network technician or the person in charge of the internal network.