What is the best course of action when a server is down?
If you aren't able to access a server, there are a few quick tests you can do to determine if the machine is completely offline or if there is a problem with just the websites. If pages aren't working well in a browser you can try to access WHM or cPanel with the IP address of the machine to see if that allows you to access those areas of the system. If that works, the problem may be limited to just the web service on the machine. If you can't access WHM at all, you can try pining the IP address of the server to see if it responds. You can do this from your local computer with this command:
where "18.104.22.168" is your server's IP address. If that doesn't work, it's possible the machine is completely offline, and in that case, you would need to speak with your hosting provider or data center to see if they can get you more details on the issue.
If you're not sure who your hosting provider is, the following article should be helpful with identifying who they are: