HA with insufficent capacity in cluster

We had a HA Cluster with two Host 5.1, all VM run in the first host (12 VMs), and vCenter Appliance Linux.

When we disconnected of the energy the first host (shut down simulation), the second host only restart 4 VMs (including the vCenter Virtual Appliance), and the vCenter show the message "Insufficient capacity in cluster HA_CLUSTER1 to satisfy resource configuration in MY_DATACENTER"

We had configured the HA with "Specify failover host" and don't work, we try with "percentage of cluster resources: 50%" but, is the same error.

We has only two host  in the Cluster.

Thanks in advance