New Customers:

If you are trying to access your Control Panel via http://yourdomain/cpanel, you will not be able to until your Domain resolves. (24-72 hours)

You can however login via IP address while you wait for it to resolve.

Check your welcome email for the IP address your site uses and the exact url to your temporary control panel. If you have lost that email, contact us and we will look it up for you.

Login with the user and password that were sent to you in your welcome email. 

Existing customers:

If you are receiving an error that the page could not be displayed when trying to log into the control panel, It is most likely due to the fact that your firewall is blocking the port that the control panel uses.

If you used your office PC or cyber cafe, normally it's inaccessible, because their firewall have blocked cpanel's port. Port that is used to access the server is :- 21 (ftp), 2082/2083 (cpanel) and 2095/2096 (webmail).
 
There is no solution for this kind of problem, because it is caused by your own PC. However, you may follow the below suggestion :-

1) If you use office PC, you can check with the PC technician to enable the above ports.
 
2) Use your own PC (at home).

Kindly also see: https://billing.netkl.com/knowledgebase.php?action=displayarticle&catid=9&id=37