This answer comes courtesy of virtualization expert Rick Vanover:
Adding servers to a VMware Infrastructure 3 (VI3) cluster is usually a non-event. In the case of certain functions not working correctly for unexplained reasons, we can employ a few approaches correct the problem.
First thing, check domain name system (DNS). VMware HA, as well as all ESX to vCenter communication, is extremely dependent on accurate name resolution. One configuration that has caused problems for me is not getting all relevant DNS suffixes or DNS servers listed on the configuration of the host.
If that still doesn’t work, you should consider rebuilding the host. This could be reinstalling ESX, or taking it out and putting another host in to see if the cluster can function with a different host. On VMware communities, there also are some comments about host names that are extremely long. So in the interest of testing, keep the host name less than 13 characters or so in order to be safe.