Your cPanel control panel is accessible via any of the following links:

https://yourdomain.com/cpanel
https://yourdomain.com:2082
https://yourip:2082

Kindly note that "yourdomain.com" should be replaced with your actaul domain.

Your control panel/s run on ports 2082 (cPanel), so if you are behind a firewall or a proxy server you might have trouble accessing your control panel if that port is blocked. Unfortunately, there is no way around this and the only resolution is to talk to your Network Administrator about opening up that port for you.