#Requires -Version 5.1
<#
    JbTecWiz Support Centre -- read-only diagnostic

    Fault : A Group Policy setting is not applying and gpresult does not explain why
    Source: https://jbtecwiz.com/support/srv-id-gpo-not-applying

    This script CHANGES NOTHING. It runs only the inspection commands
    from the write-up -- the Get-, Test- and Resolve- calls that
    establish which cause is in play -- and prints what each returned.
    Anything that writes, deletes, starts or stops is excluded by
    construction, not by judgement.

    Read the output alongside the write-up, then pick the fix that
    matches. Each fix has its own script on the same page.

    --------------------------------------------------------------------
    NO WARRANTY - USE AT YOUR OWN RISK

    This script is provided by JbTecWiz as-is and with no warranty of any
    kind, express or implied. You run it entirely at your own risk.

    JbTecWiz accepts no liability for any loss or damage arising from its
    use, including but not limited to data loss, downtime, or configuration
    changes that turn out to be wrong for your system.

    You are responsible for reading this script before running it, for
    satisfying yourself that it suits the machine in front of you, and for
    having a working backup first. Some steps cannot be undone.
    --------------------------------------------------------------------
#>

[CmdletBinding()] param([switch]$Transcript)
$ErrorActionPreference = 'Continue'

if ($Transcript) {
    $log = Join-Path $env:USERPROFILE ("jbtecwiz-srv-id-gpo-not-applying-" + (Get-Date -Format yyyyMMdd-HHmmss) + ".txt")
    Start-Transcript -Path $log | Out-Null
    Write-Host ('  Saving a transcript to ' + $log)
}

function Write-Rule { param([string]$Text)
    Write-Host ''
    Write-Host ('-' * 70) -ForegroundColor DarkGray
    if ($Text) { Write-Host $Text -ForegroundColor Cyan }
}

function Probe { param([string]$Label, [string]$Fix, [scriptblock]$Command)
    Write-Rule ("  " + $Label)
    Write-Host ("  from: " + $Fix) -ForegroundColor DarkGray
    Write-Host ''
    foreach ($l in ($Command.ToString().Trim() -split "`n")) {
        Write-Host ("    " + $l.Trim()) -ForegroundColor DarkGreen
    }
    Write-Host ''
    try {
        $out = & $Command 2>&1 | Out-String
        if ([string]::IsNullOrWhiteSpace($out)) {
            Write-Host '    (returned nothing)' -ForegroundColor DarkGray
        } else {
            foreach ($l in ($out.TrimEnd() -split "`n")) { Write-Host ("    " + $l.TrimEnd()) }
        }
    } catch {
        Write-Host ("    could not run: " + $_.Exception.Message) -ForegroundColor Yellow
    }
}

Write-Rule
Write-Host '  A Group Policy setting is not applying and gpresult does not explain why' -ForegroundColor White
Write-Host '  Read-only diagnostic -- nothing is changed.' -ForegroundColor Green
Write-Rule

Probe -Label 'Check the user object is in an OU the policy is linked to. A user in a different OU from their computer is the most common cause of a user policy not applying.' -Fix 'Check the user side of processing' -Command {
    Get-ADUser jbloggs | Select-Object DistinguishedName
    Get-GPInheritance -Target 'OU=Users,OU=Site,DC=example,DC=local' | Select-Object -ExpandProperty InheritedGpoLinks
}

Probe -Label 'Test any WMI filter directly on the client -- a filter that returns nothing silently excludes the policy.' -Fix 'Check the computer side and the WMI filter' -Command {
    Get-CimInstance -Query "SELECT * FROM Win32_OperatingSystem WHERE ProductType = '3'"
}

Write-Rule
Write-Host '  Diagnostic finished. Nothing was changed.' -ForegroundColor Green
Write-Host ''
Write-Host '  Compare the output above with the write-up, then run the'
Write-Host '  script for the fix that matches:'
Write-Host '    https://jbtecwiz.com/support/srv-id-gpo-not-applying'
Write-Rule
if ($Transcript) { Stop-Transcript | Out-Null }