PSCustomObject Not Assigning Data

[ICTPSOSSPA]

I am having issues where I am unable to assign the value of the variable $Folder_Access_Check.Identity to an array.
Outside of Powershell Studio 2023 (in ISE) I have the same code working without issue and I'm trying to move it to a GUI but can't seem to work around this issue. Any advice would be appreciated

Code: [Select all] [Expand/Collapse] [Download] (UserAccessCheck.ps1)

1.    
2. $DATA_ACLS = RandomName
3. $Folder_Access_Checks = Get-Acl $FolderPath | ForEach-Object { $_.Access } | Select-Object -Property @{ n = "Identity"; e = { $_.IdentityReference.ToString().Split("\")[1] } }
4.    
5.     If ($cmb_organisations.Text -eq "My Org")
6.     {
7.         Foreach ($Folder_Access_Check in $Folder_Access_Checks)
8.         {
9.             If ($($Folder_Access_Check.identity) -contains $DATA_ACLS)
10.             {
11.                 $Valid_Folder_Groups += $Folder_Access_Check.Identity
12.             }
13.         }
14.     }

$Valid_Folder_Groups += $Folder_Access_Check.Identity - this is the line that fails as it's not adding the information to the $Valid_Folder_Groups variable.