Set-Location not working when called from script

I need to do some registry change where I need to give admin permission to a key. I need to provide permission to the key gpsvc (in HKLM:\SYSTEM\CurrentControlSet\services\).

I have written a script for this, but somehow the permission is not getting changed nor the path is getting set. If I execute the script line by line it works, but when I try to execute it as a script it fails.

$Cred = Get-Credential Global\admin

Invoke-WmiMethod -Path "Win32_Service.Name='RemoteRegistry'" -Name StartService -ComputerName D8CB8A200738

Enter-PSSession D8CB8A200738 -Credential $Cred

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\services\gpsvc", [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()

$acl = Get-Acl -Path "HKLM:\SYSTEM\CurrentControlSet\services\gpsvc"
$inherit = [System.Security.AccessControl.InheritanceFlags]"ContainerInherit, ObjectInherit"
$propagation = [System.Security.AccessControl.PropagationFlags]"None"
$rule = New-Object System.Security.AccessControl.RegistryAccessRule ".\Administrators", "FullControl", $inherit, $propagation, "Allow"
$acl.AddAccessRule($rule)
$acl | Set-Acl

pushd
Set-Location HKLM:\SYSTEM\CurrentControlSet\services

Output:

Thanks for you comments and feedback. I have the final solution here.

$ws = “2DD8CB8A2009482”

$Global:cred = Get-Credential -Credential global\admin

$Winsvc = Get-WmiObject -Class Win32_Service -Computer $ws `
         -Filter "Name='WinRM'" -ErrorAction SilentlyContinue `
         -Credential $cred

$Winsvc.changestartmode("Auto") 

if ($Winsvc.State -eq 'Stopped')
{

    Try{
        $Winsvc.StartService()
       }
    Catch{
            Write-Host "Unable to start service" -ForegroundColor Red
            Break
         } 

}


Invoke-Command -ComputerName $ws -Credential $cred -ScriptBlock{


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\services\gpsvc",[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()

$acl= get-acl -path "HKLM:\SYSTEM\CurrentControlSet\services\gpsvc"
$inherit = [system.security.accesscontrol.InheritanceFlags]"ContainerInherit, ObjectInherit"
$propagation = [system.security.accesscontrol.PropagationFlags]"None"
$rule=new-object system.security.accesscontrol.registryaccessrule ".\Administrators","FullControl",$inherit,$propagation,"Allow"
$acl.addaccessrule($rule)
$acl|set-acl

}