Thanks Beni for clarification.
There can be some scenarios in those cases HA will not restart/Power on VMs.
1. Say vCPUs available on both powered on hosts are already assigned to all powered on VMs, then no more VMs can be restarted.
2. If you have dedicated some hosts for dedicated fail over and dedicated host(s) is down, HA will not power on the VMs at all
3. It also depends on how you have shutdown your hosts: Refer: http://www.yellow-bricks.com/2014/04/04/esxi-dcui-shutdown-vs-vcenter-shutdown-host/
There are 3 ways to shutdown the hosts: 1. From web client/VI client ...2. SSH session to host ...3. From DCUI ie.ILO console.
Let me know which option did you use?
4. It also depends on how "isolation response" is configured.
5. Weather LUNs/Datastores on 3rd hosts are not accessible on 2 powered on hosts (may be after you shutdown)
Can you post screen shot on HA configuration? just let me know if you are using DRS as well?