How to grace period reset with Powershell

My questions are :

1- Im trying to write a script for monitoring RDS grace period which expire in 10 days.

it does not work for Powershell.

wmic /namespace:\\root\CIMV2\TerminalServices PATH Win32_TerminalServiceSetting WHERE (__CLASS !="") CALL GetGracePeriodDays

Error :

__CLASS : The term '__CLASS' is not recognized as the name of a cmdlet

2- I am trying to take an ownership and give admins the full rights. But I am getting like below.

Error :

You cannot call a method on a null-valued expression. At line:3 char:1
+ $acl = $key.GetAccessControl()
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull   You cannot call a method on a null-valued expression. At line:5 char:1
+ $acl.SetAccessRule($rule)
+ ~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull   You cannot call a method on a null-valued expression. At line:6 char:1
+ $key.SetAccessControl($acl)
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull   Remove-ItemProperty : Requested registry access is not allowed. At line:14 char:1
+ Remove-ItemProperty -Path $keyPath -Name *L$RTMTIMEBOMB*
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : PermissionDenied: (HKEY_LOCAL_MACH...RCM\GracePeriod:String) [Remove-ItemProperty], SecurityException
    + FullyQualifiedErrorId : System.Security.SecurityException,Microsoft.PowerShell.Commands.RemoveItemPropertyCommand

Script :

try {     

$RemainingDays=(Invoke-WmiMethod -PATH (gwmi -namespace root\cimv2\terminalservices -class win32_terminalservicesetting).__PATH -name GetGracePeriodDays).daysleft
if(($RemainingDays) -and  $RemainingDays -le 10){

$regpath = "HKLM:\SYSTEM\CurrentControlSet\Control\Terminal Server\RCM\GracePeriod"
$key = [Microsoft.Win32.Registry]::LocalMachine.OpenSubKey($regpath,[Microsoft.Win32.RegistryKeyPermissionCheck]::ReadWriteSubTree,[System.Security.AccessControl.RegistryRights]::ChangePermissions)
$acl = $key.GetAccessControl()
$rule = New-Object System.Security.AccessControl.RegistryAccessRule ("SERVERNAME\Administrators","FullControl","Allow")
$acl.SetAccessRule($rule)
$key.SetAccessControl($acl)


# The target registry key's full path.
$keyPath = 'HKLM:\SYSTEM\CurrentControlSet\Control\Terminal Server\RCM\GracePeriod'

# Pass the value name pattern to Remove-ItemProperty's -Name parameter.
# Remove `-WhatIf` if the preview suggests that the operation works as intended.
Remove-ItemProperty -Path $keyPath -Name *L$RTMTIMEBOMB*

Restart-Computer -Force

}



}

catch [System.Management.Automation.RuntimeException] {
    $Exception = $_
}

LAST UPDATE :

try {     

$RemainingDays=(Invoke-WmiMethod -PATH (gwmi -namespace root\cimv2\terminalservices -class win32_terminalservicesetting).__PATH -name GetGracePeriodDays).daysleft

if(($RemainingDays) -and  $RemainingDays -le 10){

function enable-privilege {
 param(
  ## The privilege to adjust. This set is taken from
  ## http://msdn.microsoft.com/en-us/library/bb530716(VS.85).aspx
  [ValidateSet(
   "SeAssignPrimaryTokenPrivilege", "SeAuditPrivilege", "SeBackupPrivilege",
   "SeChangeNotifyPrivilege", "SeCreateGlobalPrivilege", "SeCreatePagefilePrivilege",
   "SeCreatePermanentPrivilege", "SeCreateSymbolicLinkPrivilege", "SeCreateTokenPrivilege",
   "SeDebugPrivilege", "SeEnableDelegationPrivilege", "SeImpersonatePrivilege", "SeIncreaseBasePriorityPrivilege",
   "SeIncreaseQuotaPrivilege", "SeIncreaseWorkingSetPrivilege", "SeLoadDriverPrivilege",
   "SeLockMemoryPrivilege", "SeMachineAccountPrivilege", "SeManageVolumePrivilege",
   "SeProfileSingleProcessPrivilege", "SeRelabelPrivilege", "SeRemoteShutdownPrivilege",
   "SeRestorePrivilege", "SeSecurityPrivilege", "SeShutdownPrivilege", "SeSyncAgentPrivilege",
   "SeSystemEnvironmentPrivilege", "SeSystemProfilePrivilege", "SeSystemtimePrivilege",
   "SeTakeOwnershipPrivilege", "SeTcbPrivilege", "SeTimeZonePrivilege", "SeTrustedCredManAccessPrivilege",
   "SeUndockPrivilege", "SeUnsolicitedInputPrivilege")]
  $Privilege,
  ## The process on which to adjust the privilege. Defaults to the current process.
  $ProcessId = $pid,
  ## Switch to disable the privilege, rather than enable it.
  [Switch] $Disable
 )

 ## Taken from P/Invoke.NET with minor adjustments.
 $definition = @'
 using System;
 using System.Runtime.InteropServices;

 public class AdjPriv
 {
  [DllImport("advapi32.dll", ExactSpelling = true, SetLastError = true)]
  internal static extern bool AdjustTokenPrivileges(IntPtr htok, bool disall,
   ref TokPriv1Luid newst, int len, IntPtr prev, IntPtr relen);

  [DllImport("advapi32.dll", ExactSpelling = true, SetLastError = true)]
  internal static extern bool OpenProcessToken(IntPtr h, int acc, ref IntPtr phtok);
  [DllImport("advapi32.dll", SetLastError = true)]
  internal static extern bool LookupPrivilegeValue(string host, string name, ref long pluid);
  [StructLayout(LayoutKind.Sequential, Pack = 1)]
  internal struct TokPriv1Luid
  {
   public int Count;
   public long Luid;
   public int Attr;
  }

  internal const int SE_PRIVILEGE_ENABLED = 0x00000002;
  internal const int SE_PRIVILEGE_DISABLED = 0x00000000;
  internal const int TOKEN_QUERY = 0x00000008;
  internal const int TOKEN_ADJUST_PRIVILEGES = 0x00000020;
  public static bool EnablePrivilege(long processHandle, string privilege, bool disable)
  {
   bool retVal;
   TokPriv1Luid tp;
   IntPtr hproc = new IntPtr(processHandle);
   IntPtr htok = IntPtr.Zero;
   retVal = OpenProcessToken(hproc, TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY, ref htok);
   tp.Count = 1;
   tp.Luid = 0;
   if(disable)
   {
    tp.Attr = SE_PRIVILEGE_DISABLED;
   }
   else
   {
    tp.Attr = SE_PRIVILEGE_ENABLED;
   }
   retVal = LookupPrivilegeValue(null, privilege, ref tp.Luid);
   retVal = AdjustTokenPrivileges(htok, false, ref tp, 0, IntPtr.Zero, IntPtr.Zero);
   return retVal;
  }
 }
'@

 $processHandle = (Get-Process -id $ProcessId).Handle
 $type = Add-Type $definition -PassThru
 $type[0]::EnablePrivilege($processHandle, $Privilege, $Disable)
}

enable-privilege SeTakeOwnershipPrivilege 
$key = [Microsoft.Win32.Registry]::LocalMachine.OpenSubKey("SYSTEM\CurrentControlSet\Control\Terminal Server\RCM\GracePeriod",[Microsoft.Win32.RegistryKeyPermissionCheck]::ReadWriteSubTree,[System.Security.AccessControl.RegistryRights]::takeownership)
# You must get a blank acl for the key b/c you do not currently have access
$acl = $key.GetAccessControl([System.Security.AccessControl.AccessControlSections]::None)
$me = [System.Security.Principal.NTAccount]"Administrators"
$acl.SetOwner($me)
$key.SetAccessControl($acl)

# After you have set owner you need to get the acl with the perms so you can modify it.
$acl = $key.GetAccessControl()
$rule = New-Object System.Security.AccessControl.RegistryAccessRule ("Administrators","FullControl","Allow")
$acl.SetAccessRule($rule)
$key.SetAccessControl($acl)

$key.Close()


# The target registry key's full path.
$keyPath = 'HKLM:\SYSTEM\CurrentControlSet\Control\Terminal Server\RCM\GracePeriod'

# Pass the value name pattern to Remove-ItemProperty's -Name parameter.
# Remove `-WhatIf` if the preview suggests that the operation works as intended.
Remove-ItemProperty -Path $keyPath -Name *L$RTMTIMEBOMB*

Restart-Computer -Force

}



}

catch [System.Management.Automation.RuntimeException] {
    $Exception = $_
}

Use Get-WmiObject to perform WMI object retrieval in Powershell. In your case this would be something like:

$ts = Get-WmiObject -Class Win32_TerminalServiceSetting -Namespace "root\CIMV2\TerminalServices" $RemainingDays = $ts.GetGracePeriodDays()

<rest of your script here>