In the even of a host failure in a vSphere HA enable cluster, virtual machine will be migrated to another healthy host but stays powered off. These virtual machines staying powered off are configured with VM Override Settings.
Virtual machines with VM restart priority set to disabled will not be powered on during a HA failover event.
An event similar to the following will be posted at the cluster level confirming the decision not to power on the virtual machine.
vSphere HA did not attempt to restart <VM_NAME> in cluster <CLUSTER_NAME> in <DATACENTER_NAME> because its VM restart priority is Disabled
Virtual machine <VM_NAME> is connected
<VM_NAME> on <HOST_NAME> in <CLUSTER_NAME> is powered off
This is expected behavior when a virtual machine is configured with VM Override Settings and VM Restart priority is set to "disabled"
If virtual machine is expected to be powered on by vSphere HA in the event of host failure/isolation, VM Overrides settings for the virtual machine need to be updated as required.
Read the section "Customize an Individual Virtual Machine" from vSphere Documentation on how to manage the VM Override Settings.
Additional Read related to host failure response during HA failure. Respond to Host Failure