The vSphere HA agent on a host is in the Host Failed state. User intervention is required to resolve the situation.
Usually, such reports indicate that a host has actually failed, but failure reports can sometimes be incorrect. A failed host reduces the available capacity in the cluster and, in the case of an incorrect report, prevents vSphere HA from protecting the virtual machines running on the host.
This host state is reported when the vSphere HA primary host to which vCenter Server is connected is unable to communicate with the host and with the heartbeat datastores that are in use for the host. Any storage failure that makes the datastores inaccessible to hosts can cause this condition if accompanied by a network failure.
Check for the noted failure conditions and resolve any that are found.