"The property cannot be found on this object. Verify that the property exists." Property definitely exists

Question

I can't figure out why I am not able to change these variables. If I type them into the console in debug mode, then it prints the values. It is also strange how I am able to change the allowedRequestors variable on line 24, but not any of the others. Does anyone know why this is happening to the other variables?

$FilePath = "C:\Users\Desktop\TestScripts\testBulkAP.csv"

$headers = & $PSScriptRoot\GetToken.ps1

## preparing create Catalog data
$accesspacakgeRequest = '{"displayName":"","description":"sddsds","isHidden":false,"catalogId":"","accessPackageResourceRoleScopes":[],"accessPackageAssignmentPolicies":[{"displayName":"Initial Policy","description":"Initial Policy","durationInDays":365,"expirationDateTime":null,"canExtend":false,"requestApprovalSettings":null,"accessReviewSettings":null,"notificationSettings":null,"additionalInfo":null,"isDenyPolicy":false,"id":"","activeAssignmentCount":0,"accessPackageId":"00000000-0000-0000-0000-000000000000","accessPackageCatalog":null,"createdDateTime":null,"modifiedDateTime":null,"createdBy":"","modifiedBy":"","countOfUsersIncludedInPolicy":null,"requestorSettings":{"acceptRequests":true,"scopeType":"NoSubjects","allowedRequestors":[],"isOnBehalfAllowed":false},"questions":[]}]}'
$emlRequestUrl = "https://graph.microsoft.com/beta/identityGovernance/entitlementManagement/accessPackages"
$accesspacakgeRequestObject = ConvertFrom-Json -InputObject $accesspacakgeRequest

$Content = Import-Csv $FilePath

foreach($assignmentData in $Content) {
    $accesspacakgeRequestObject.catalogId = $assignmentData.catalogId
    $accesspacakgeRequestObject.displayName = $assignmentData.displayName
    $accesspacakgeRequestObject.description = $assignmentData.description
    $accesspacakgeRequestObject.accessPackageAssignmentPolicies.requestorSettings.scopeType = $assignmentData.scope 

    if ($assignmentData.scope -eq "SpecificDirectorySubjects") {
    $accesspacakgeRequestObject.accessPackageAssignmentPolicies.requestorSettings.allowedRequestors += New-Object -TypeName psobject -Property @{'@odata.type' = '#microsoft.graph.groupMembers'; 'id' = $assignmentData.groupId; 'description' = $assignmentData.groupName; 'isBackup' = 'false'}
    }

    $numApprovalStages = [int]$assignmentData.approvalStages

    if ($numApprovalStages -gt 0) {
    $accesspacakgeRequestObject.accessPackageAssignmentPolicies.requestApprovalSettings += New-Object -TypeName psobject -Property @{'approvalMode' = 'Serial'; 'isApprovalRequired' = 'true'; 'isApprovalRequiredForExtension' = 'false'; 'isRequestorJustificationRequired' = 'false'; 'approvalStages' = @()}

    for ($i=1;$i -le [int]$assignmentData.approvalStages; $i++)
    {
        $accesspacakgeRequestObject.accessPackageAssignmentPolicies.requestApprovalSettings.approvalStages += New-Object -TypeName psobject -Property @{'approvalStageTimeOutInDays' = '14'; 'primaryApprovers' = @(); escalationApprovers = @();'isEscalationEnabled' = 'false'; 'escalationTimeInMinutes' = '0'; 'isApproverJustificationRequired' = 'true'}
        $accesspacakgeRequestObject.accessPackageAssignmentPolicies.requestApprovalSettings.approvalStages.primaryApprovers += New-Object -TypeName psobject -Property @{'@odata.type' = '#microsoft.graph.singleUser'; "displayName" = ''; 'objectId' = Get-Variable -Name "assignmentData.approver$1" -ValueOnly; 'isBackup' = 'false'}
        
    }

    }
    
    
    
    $requestbody = $accesspacakgeRequestObject | ConvertTo-Json -Depth 10
    $response = Invoke-RestMethod $emlRequestUrl -Headers $headers -Method Post -Body $requestbody -UseBasicParsing -ErrorAction Continue
}

The error message is:

The property 'requestApprovalSettings' cannot be found on this object. Verify that the property exists and can be set.
At C:\Users\Desktop\TestScripts\AddAccessPackageAndPolicyWITHAPPROVER.ps1:30 char:5
+     $accesspacakgeRequestObject.accessPackageAssignmentPolicies.reque ...
+     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : PropertyAssignmentException
 
The property 'approvalStages' cannot be found on this object. Verify that the property exists and can be set.
At C:\Users\Desktop\TestScripts\AddAccessPackageAndPolicyWITHAPPROVER.ps1:34 char:9
+         $accesspacakgeRequestObject.accessPackageAssignmentPolicies.r ...
+         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : PropertyNotFound
 
Get-Variable : Cannot find a variable with the name 'assignmentData.approver1'.
At C:\Users\Desktop\TestScripts\AddAccessPackageAndPolicyWITHAPPROVER.ps1:35 char:250
+ ... objectId' = Get-Variable -Name "assignmentData.approver$i" -ValueOnly ...
+                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (assignmentData.approver1:String) [Get-Variable], ItemNotFoundException
    + FullyQualifiedErrorId : VariableNotFound,Microsoft.PowerShell.Commands.GetVariableCommand
 
The property 'primaryApprovers' cannot be found on this object. Verify that the property exists and can be set.
At C:\Users\Desktop\TestScripts\AddAccessPackageAndPolicyWITHAPPROVER.ps1:35 char:250
+ ... objectId' = Get-Variable -Name "assignmentData.approver$i" -ValueOnly ...
+                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : PropertyNotFound

Answer 1

The .accessPackageAssignmentPolicies property contains an array ([...]-enclosed in the JSON input).

Even though that array happens to contain only one element, you still need to access it by index in order to set its (only) element's properties; e.g.:

# Note the `[0]`
$accesspacakgeRequestObject.accessPackageAssignmentPolicies[0].requestorSettings.scopeType = $assignmentData.scope 

Note that getting properties does not strictly require this index access, because of a feature called member-access enumeration.

This perhaps surprising asymmetry - requiring indexed access on setting - is by design, however - see this answer for more information.