If VMware HA doesn’t work.

Verify that host name is lowercase: hostname; hostname -s
Verify that host name in /etc/hosts is lowercase
Verify that search domain in /etc/resolv.conf is in lowercase
Verify that host name in /etc/sysconfig/network is fqdn, all lowercase
Verify that the host name in esx.conf is fqdn, all lowercase
Verify that host name in DNS is lowercase: nslookup; <short hostname> (should properly resolve fqdn of host, all lowercase)
Verify that all primary service consoles have the same name.
Verify that all primary service consoles are in the same IP subnet.
If VMotion vmkernel port is on same vSwitch as primary service console, use das.allowVmotionNetworks=1
If host has multiple service consoles, use KB 1006541 and the das.allowNetwork0 HA option to ensure that only the primary service console is allowed.
Verify that customer has appropriate licensing for HA, and has available licenses: In LM Tools, perform a status inquiry, verify that cu is licensed for VC_DAS
Once you have met all of the above criteria, enable HA.
If, after you have verified all the above, and HA still won’t configure:
On the host, stop vpxa: service vmware-vpxa stop
The host will show not responding in VC after a while
Disconnect the host from VC
Re-connect the host to VC
This will force the VPXA package to re-deploy, as well as the HA packages to re-deploy.
Re-configure the hosts for HA.

System Administrator