When you encounter issues with the network connectivity, it's better to take it one step at a time to find the error.
Firstly, check the firewall on the computer that's trying to connect. Make sure that's either turned off or the application is allowed to communicate with Internet. Secondly, start the application (client) used to connect and verify that the server and port is configured properly. Before connecting, access Device Manager and install all the missing drivers. Eventually, right click the network adapters, disable them and then re-enable. If you still have problems, contact your local IT administrator. There is a possibility the server is offline, therefore connecting is impossible until it comes back online.