Exchange 2013 CU 23 failed

HI, I am upgrading my exchange 2013 to CU 23 and its getting failed with below error, i have also followed below mentioned link...

Error:

The following error was generated when "$error.Clear();
$BEVdirIdentity = $RoleNetBIOSName + "\OAB (Exchange Back End)";
$be = get-OabVirtualDirectory -ShowMailboxVirtualDirectories -Identity $BEVdirIdentity -DomainController $RoleDomainController -ErrorAction SilentlyContinue;
if ($be -eq $null)
{
new-OabVirtualDirectory -Role Mailbox -WebSiteName "Exchange Back End" -DomainController $RoleDomainController;
}
set-OabVirtualdirectory -Identity $BEVdirIdentity -InternalUrl $null -ExternalUrl $null;
. "$RoleInstallPath\Scripts\Update-AppPoolManagedFrameworkVersion.ps1" -AppPoolName:"MSExchangeOABAppPool" -Version:"v4.0";
" was run: "System.Runtime.InteropServices.COMException (0x80070003): The system cannot find the path specified.

at System.DirectoryServices.DirectoryEntry.Bind(Boolean throwIfFail)
at System.DirectoryServices.DirectoryEntry.Bind()
at System.DirectoryServices.DirectoryEntry.get_AdsObject()
at System.DirectoryServices.PropertyValueCollection.PopulateList()
at System.DirectoryServices.PropertyValueCollection..ctor(DirectoryEntry entry, String propertyName)
at System.DirectoryServices.PropertyCollection.get_Item(String propertyName)
at Microsoft.Exchange.Management.Metabase.IisUtility.CheckForAuthenticationMethod(DirectoryEntry virtualDirectory, AuthenticationMethodFlags method, Boolean ignoreAnonymousOnCert)
at Microsoft.Exchange.Management.SystemConfigurationTasks.SetOabVirtualDirectory.StampChangesOn(IConfigurable dataObject)
at Microsoft.Exchange.Configuration.Tasks.SetObjectTaskBase`2.PrepareDataObject()
at Microsoft.Exchange.Management.SystemConfigurationTasks.SetVirtualDirectory`1.PrepareDataObject()
at Microsoft.Exchange.Management.SystemConfigurationTasks.SetExchangeVirtualDirectory`1.PrepareDataObject()
at Microsoft.Exchange.Management.SystemConfigurationTasks.SetOabVirtualDirectory.PrepareDataObject()
at Microsoft.Exchange.Configuration.Tasks.SetTaskBase`1.InternalValidate()
at Microsoft.Exchange.Configuration.Tasks.SetSystemConfigurationObjectTask`3.InternalValidate()
at Microsoft.Exchange.Management.SystemConfigurationTasks.SetExchangeVirtualDirectory`1.InternalValidate()
at Microsoft.Exchange.Management.SystemConfigurationTasks.SetOabVirtualDirectory.InternalValidate()
at Microsoft.Exchange.Configuration.Tasks.Task.<ProcessRecord>b__b()
at Microsoft.Exchange.Configuration.Tasks.Task.InvokeRetryableFunc(String funcName, Action func, Boolean terminatePipelineIfFailed)
at Microsoft.Exchange.Configuration.Tasks.Task.ProcessTaskStage(TaskStage taskStage, Action initFunc, Action mainFunc, Action completeFunc)
at Microsoft.Exchange.Configuration.Tasks.Task.ProcessRecord()
at System.Management.Automation.CommandProcessor.ProcessRecord()".