I'm going to start something new at EE, Tips from the VMware vSphere Datacentre... real world tips, that get you through that tricky moment, when all things are turning to that brown stuff.... This happened to me today, adding 5 new vSphere ESXi hosts to a Cluster of 150.

Andy's VMware vSphere tip#1 - HA Operation Timeout - A Host or Hosts refuse to bring HA (High Avaibility online), after upgrading vCenter Server, or adding new hosts to vCenter Server datacentre, no matter what you try, you obtain an Operation Time Out, you look at the FDM.log as advised here - https://kb.vmware.com/s/article/2011974.

Solution. - Just Edit Cluster Settings - and Disable and Re-enable vSphere HA.

Simples! All that work browsing logs and Reconfigure HA for the Host not required. This does not affect any VMs, and HA will just be unavailable for 30 seconds why you turn on and off.

If you need to discuss this, please post a question to the VMware topic area.