You may see an error like the following.
zone domain.tld/IN: NS 'ns1.domain.tld' has no address records (A or AAAA)
zone domain.tld/IN: not loaded due to errors.
This error indicates that the zone is not being loaded because there is an NS record that is a subdomain of the zone that does not have a corrisponding A or AAAA record. This means that the zone's nameserver will not resolve and as such, the zone is not loaded.
An A or AAAA record will need to be added for the offending NS record. This can be done from the following locations in WHM and cPanel.
Home » DNS Functions » DNS Zone Manager