Symptoms
Within the DNS Clusters interface of WHM, you may find that a DNS Cluster reports the following error:
Could not communicate with remote API server.
Description
The message could appear for various reasons, though the two most common would be:
1. The DNS clusters are unable to communicate with one another due to connectivity issues.
2. The DNS Clusters do not have a "Reverse Trust" setup, and are set to "synchronize" between one another.
Workaround
To address the first issue, we recommend testing whether both servers can communicate with one another. From both servers, perform:
telnet 192.168.0.2 2087
Please note that the above IP address is an example IP address. The IP must be replaced if you wish to test connectivity between your servers.
Ensure that you change the server's IP that you are testing, depending on which server you accessed.
If your servers can communicate with one another, then the issue may be that a "Reverse Trust Relationship" has not been established between both servers.
You must set up a Reverse Trust relationship between each server in a DNS cluster. This relationship allows servers in a DNS cluster to share records. Reverse trust is only required if the DNS Cluster relationship is set to "synchronize."
For further information on DNS Cluster setups, please refer to this document.
https://docs.cpanel.net/knowledge-base/dnsonly/guide-to-dns-cluster-configurations/