Trying to retrieve External Network IP Address from specific vapp

I know this should be simple but having an issue.  vCD 5.1 

trying to use this script in the vmware help to get a list i can copy and paste into excel to retrieve the vm name and external ip from an individual vapp:

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$myOrg = Get-Org -Name 'Org1'

$vApps = Get-CIVApp -Org $myOrg

$vAppNetworkAdapters = @()

foreach ($vApp in $vApps) {

        $vms = Get-CIVM -VApp $vApp

        foreach ($vm in $vms) {

                $networkAdapters = Get-CINetworkAdapter -VM $vm

                foreach ($networkAdapter in $networkAdapters) {

                        $vAppNicInfo = New-Object "PSCustomObject"

                        $vAppNicInfo | Add-Member -MemberType NoteProperty -Name VAppName -Value $vApp.Name

                        $vAppNicInfo | Add-Member -MemberType NoteProperty -Name VMName   -Value $vm.Name

                        $vAppNicInfo | Add-Member -MemberType NoteProperty -Name NIC      -Value ("NIC" + $networkAdapter.Index)

                        $vAppNicInfo | Add-Member -MemberType NoteProperty -Name ExternalIP -Value $networkAdapter.IpAddress

                        $vAppNicInfo | Add-Member -MemberType NoteProperty -Name InternalIP -Value $networkAdapter.ExternalIpAddress

                        $vAppNetworkAdapters += $vAppNicInfo

                 }     

         }

}

$vAppNetworkAdapters

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chopped it down to this:

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$vms = Get-CIVM -VApp 'vApp1'

        foreach ($vm in $vms) {

                $networkAdapters = Get-CINetworkAdapter -VM $vm

                foreach ($networkAdapter in $networkAdapters) {

                       $vAppNicInfo = New-Object "PSCustomObject"

#                        $vAppNicInfo | Add-Member -MemberType NoteProperty -Name VAppName -Value $vApp.Name

                        $vAppNicInfo | Add-Member -MemberType NoteProperty -Name VMName   -Value $vm.Name

                        $vAppNicInfo | Add-Member -MemberType NoteProperty -Name NIC      -Value ("NIC" + $networkAdapter.Index)

                        $vAppNicInfo | Add-Member -MemberType NoteProperty -Name ExternalIP -Value $networkAdapter.IpAddress

                        $vAppNicInfo | Add-Member -MemberType NoteProperty -Name InternalIP -Value $networkAdapter.ExternalIpAddress

                        $vAppNetworkAdapters += $vAppNicInfo

                 }     

         }

$vAppNetworkAdapters

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but getting these errors:

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Method invocation failed because [System.Management.Automation.PSObject] doesn't contain a method named 'op_Addition'.

At C:\scripts\nets.ps1:12 char:48

+                         $vAppNetworkAdapters += <<<<  $vAppNicInfo

    + CategoryInfo          : InvalidOperation: (op_Addition:String) [], RuntimeException

    + FullyQualifiedErrorId : MethodNotFound