Problem while creating VM using packer

Packer
1

Hi,

I am trying to create new VM using packer. I am using below json file. When I run packer tool with command ./packer build -debug packer_iso_1_1.json , I get below error, could you please suggest what could be the problem :

Debug mode enabled. Builds will not be parallelized.
vsphere-iso: output will be in this color.

==> vsphere-iso: Pausing after run of step ‘StepConnect’. Press enter to continue.
==> vsphere-iso: Creating VM…

==> vsphere-iso: Pausing after run of step ‘StepCreateVM’. Press enter to continue. ==> vsphere-iso: Customizing hardware…
==> vsphere-iso: Pausing before cleanup of step ‘StepCreateVM’. Press enter to continue.
==> vsphere-iso: Destroying VM…
==> vsphere-iso: Pausing before cleanup of step ‘StepConnect’. Press enter to continue.
Build ‘vsphere-iso’ errored: ServerFaultCode:
Unexpected element tag “nestedHVEnabled” seen

while parsing serialized DataObject of type vim.vm.ConfigSpec
at line 2, column 141

while parsing call information for method ReconfigVM_Task
at line 2, column 66

while parsing SOAP body
at line 2, column 60

while parsing SOAP envelope
at line 2, column 0

while parsing HTTP request for method reconfigure
on object of type vim.VirtualMachine
at line 1, column 0

==> Some builds didn’t complete successfully and had errors:
–> vsphere-iso: ServerFaultCode:
Unexpected element tag “nestedHVEnabled” seen

while parsing serialized DataObject of type vim.vm.ConfigSpec
at line 2, column 141

while parsing call information for method ReconfigVM_Task
at line 2, column 66

while parsing SOAP body
at line 2, column 60

while parsing SOAP envelope
at line 2, column 0

while parsing HTTP request for method reconfigure
on object of type vim.VirtualMachine
at line 1, column 0

==> Builds finished but no artifacts were created.

Below is json file I am using
{
“builders”: [
{
“type”: “vsphere-iso”,

  "vcenter_server":      "address",
  "username":            "root",
  "password":            "password",
  "insecure_connection": "true",
  "vm_name": "VikasTest1",
  "host": "hostaddress",
  "guest_os_type": "rhel6_64Guest",
   "ssh_username": "root",
  "ssh_password": "password",
  "datastore": "delv3-datastore3",
  "network": "LR-15.119.156.X",
   "CPUs":             4,
   "cpu_cores": 2,
  "RAM":              8192,
  "RAM_reserve_all": true,
  "disk_controller_type":  "pvscsi",
  "disk_size":       16384,
  "disk_thin_provisioned": true,
  "network_card": "vmxnet3",
  "iso_paths": [
    "[delv3-datastore1] RHEL6.8/INTERNAL_USE_LABONLY_UNSUPPORTED_DONOT_DELIVER_BOOT_DVD_JA286-15043.iso"
   ],
  "floppy_files": [
    "/usr/local/packer/preseed.cfg"
  ]

}

],
“provisioners”: [
{
“type”: “shell”,
“inline”: [“ls /”]
}
]

}