When attempting to install cPanel you receive the following notice, and the installation fails:
(DEBUG): Retrieving http://httpupdate.cpanel.net/cpanelsync/TIERS to the TIERS file...
(FATAL): The system could not fetch the TIERS file:
When attempting to reach the noted URL using curl it returns something similar to the following:
This transfer is blocked.
This occurs as a result of your Web Appliance Firewall (WAF), or other security appliance, blocking the requests.
To work around this behavior either whitelist the cpanel.net domain space in your appliance (*.cpanel.net* or similar), or temporarily disable the WAF