Unable to create a function to get nested groups

I am a beginner programmer in PowerHhell. I am trying to create a function that outputs all nested groups of a group. When I run the function, it gives an error:

Get-ADGroupMember : Cannot find an object with identity: "CN=John,OU=Test,OU=Company,DC=klns,DC=ado,DC=com" в "DC=klns,DC=ado,DC=com".
D:\Work\Powershell\Folder\est4.ps1:11 symbol:23
+ $GetObjects = Get-ADGroupMember $Members
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : ObjectNotFound: (CN=John,OU=Т...C=ado,DC=com:ADGroup) [Get-ADGroupMember], ADIdentityNotFoundException
+ FullyQualifiedErrorId : ActiveDirectoryCmdlet:Microsoft.ActiveDirectory.Management.ADIdentityNotFoundException,Microsoft.ActiveDirectory.Management.Commands.GetADGroupMember

$Group = "LGR-Test-RWX"
function Get-NestedGroups
{
       
  $script:Groups = @()    
  $script:ADGroup = (Get-ADGroup -Identity $Group -Properties Name, Member).Member
  $script:Groups += $ADGroup

  foreach ($Members in $ADGroup)
    {
      $GetObjects = Get-ADGroupMember $Members
      $GetGroups = $GetObjects | Where-Object objectClass -eq "group"
        if ($GetGroups)
        {
          foreach ($Groups in $GetGroups.Member)
          {
              Get-NestedGroups $Groups
          }
      }
  }
    
  return ($script:Groups.Name | Sort-Object -Unique)    
}
Get-NestedGroups $Group

I can't understand why it doesn't work. Please explain what I am doing wrong. Thank you.

Recursion is the best way for traversing nested structures.

This is a function I've provided as solution for a request in the module Carbon.Security, Get-CPrivilege should have an option for returning the accumelated privileges

function Get-xEffectiveGroup {

    [CmdletBinding()]
    param (
        [Parameter(Mandatory)]
        [string[]]$UserPrincipalName,

        [switch]$Local,

        [switch]$Domain
    )

    Add-Type -AssemblyName System.DirectoryServices.AccountManagement

    function Get-NestedGroups {

        [CmdletBinding()]
        param (
            [Parameter(Mandatory)]
            [System.DirectoryServices.AccountManagement.Principal]$Principal
        )

        $Groups = [System.Collections.ArrayList]@()

        $Principal.GetGroups() | foreach {
            $Groups.Add($_) | Out-Null
            $Groups.Add($(Get-NestedGroups -Principal $_)) | Out-Null
        }

        return $Groups

    }#end priv function

    $Context = New-Object System.DirectoryServices.AccountManagement.PrincipalContext(
        [System.DirectoryServices.AccountManagement.ContextType]::Domain)

    $UserPrincipal = [System.DirectoryServices.AccountManagement.UserPrincipal]::FindByIdentity(
        $Context, $UserPrincipalName
    )

    $NtDomain = (
        $userprincipal.DistinguishedName.split(',') |
            where {$_.Contains('DC')}
    )[0].split('=')[-1]

    [System.Collections.ArrayList]$AllPrincipals = @()

    if ($Domain -or -not $Local) {#get domain groups
        $AllDomainGroups = Get-NestedGroups -Principal $UserPrincipal |
            select -Unique Name |
                where {-not [string]::IsNullOrEmpty($_.Name)} |
                    select @{l = 'Name'; e = {"$NtDomain\" + $_.Name} }

        if ($AllDomainGroups) {#was found
            if (($AllDomainGroups | Measure-Object).Count -eq 1) {
                $AllPrincipals.Add($AllDomainGroups) | Out-Null
            }
            if (($AllDomainGroups | Measure-Object).Count -gt 1) {
                $AllPrincipals.AddRange($AllDomainGroups) | Out-Null
            }
        }#end domain groups found

    }

    if ($Local -or -not $Domain) {#get local groups
        $LocalGroups = Get-LocalGroup | where {
            $ThisLocalGroup = $_
            $AllPrincipals.Name | where {
                    $ThisPrincipalName = $_
                    $ThisPrincipalName -in ($ThisLocalGroup | Get-LocalGroupMember).Name
                }
        }

        if ($LocalGroups) {
            if ($LocalGroups.Count -eq 1) {#ArrayLists are faster but picky
                [void]$AllPrincipals.Add(($LocalGroups | select Name))
            }
            else {
                [void]$AllPrincipals.AddRange(($LocalGroups | select Name))
            }
        }

        $UserPrincipalGroups = Get-LocalGroup | where {
                $ThisLocalGroup = $_
                ($NtDomain + '\' + $UserPrincipal.SamAccountName) -in ($ThisLocalGroup | Get-LocalGroupMember).Name
            }

        if ($UserPrincipalGroups) {
            if ($UserPrincipalGroups.Count -eq 1) {#ArrayLists are faster but picky
                [void]$AllPrincipals.Add(($UserPrincipalGroups | select Name))
            }
            else {
                [void]$AllPrincipals.AddRange(($UserPrincipalGroups | select Name))
            }
        }

    }#end Local groups

    return $AllPrincipals

<#
.SYNOPSIS
    Get all groups a domain user is member of.

.DESCRIPTION
    Get all groups (explicit and inherited and local) that a user principal object is member of.

.PARAMETER UserPrincipalName
    Domain name as domain\account to get all groups for.

.PARAMETER Local
    Only get implicit local group membership. I.e. membership through a domain group wont show.

.PARAMETER Domain
    Only get domain groups.

.EXAMPLE
    Get-xEffectiveGroup -UserPrincipalName domain\accountname

.EXAMPLE
    Get-xEffectiveGroup -UserPrincipalName domain\accountname -Local

    Show all local groups where the UserPrincipalName is an implict member. Inheritied
    membership throuhg domain groups will not show.

#>

}