Are you using a computer with a firewall? If so port 2082 and and 2095 must be open for access. You can log in at the login page by following the links below
For cPanel:
http://domain.com/cpanel
http://domain.com:2082
https://domain.com:2083
http://cpanel.domain.com
For Webmail:
http://domain.com/webmail
http://domain.com:2095
https://domain.com:2096
http:webmail.domain.com
In case these URLs fail to load, try accessing using
http://cpanel.domain.com
http://webmail.domain.com