We utilize a variety of firewalls that may block you for excessive login failures, whether that's for cpanel logins, webmail, IMAP, email programs, etc. In this case you won't be able to see your site and will need to open a ticket to get unblocked. We generally post an announcement if a server is actually down or if there is a network outage, but an easy way to check whether the site is down "just for you" is to visit a proxy site that will check.
Examples;
