Cautionary Note: We recommend users to exercise extreme caution when making changes to the server's network configuration. Please note that the server may lose network services if configured incorrectly.
If the server is offline(not responding to ping or any service connections), some form of console or KVM is needed to access the server. Typically, the hosting provider would need to advise you if that is available for your particular server.
Generally speaking, the configuration for the server's primary IP address would be within a file, depending on the primary network interface for the server.
Check that file to ensure that the "onboot" parameter is set, along with the appropriate network settings for that particular server environment.
I should note, that cPanel does require that the server operates in a static network environment, with a static IP address configured on the server:
A properly-configured Ethernet device with a static IP address and fully-qualified hostname. The system attempts to detect and set the ethernet device during the installation process.
You cannot use an IP address that a DHCP service dynamically assigns to your server."
Consult your host or network provider to find out what settings the network environment requries, then apply them within the configuration file mentioned above. If you're uncomfortable with such tasks first hand, you may consider the assistance of an administration services provider. A list of which, we have available to you at https://forums.cpanel.net/resources/categories/system-administration-services.1/?page=1