HA Agent on ESX-HOST in cluster CLUSTER-NAME has an error

If you came across this error message when configuring HA:
"HA Agent on ESX-HOST in cluster CLUSTER-NAME has an error"

First thing you will need to check is your name resolution, which is your DNS.

Try to PING each other from the ESX. If you able to do so, the next thing you probably need to check is the /etc/hosts and /etc/resolv.conf files

Especially when you have change the service console ip, the ip in /etc/hosts file most probably still point to the old ip, also the host name is case sensitive.