Running Set_WmiNamespaceSecurity.ps1 fails with "Invalid namespace"

Is this the script you are trying to run ? https://blogs.msdn.microsoft.com/wmi/2009/07/27/scripting-wmi-namespace-security-part-3-of-3/

DJ: It looks like it.

This code work well..

.\Set-WmiNamespaceSecurity.ps1 -namespace root/cimv2 -operation Add -account UserName -permissions Enable,RemoteAccess

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Ref : https://raw.githubusercontent.com/KurtDeGreeff/PlayPowershell/master/Set-WmiNamespaceSecurity.ps1

# Copyright (c) Microsoft Corporation.  All rights reserved. 
# For personal use only.  Provided AS IS and WITH ALL FAULTS.
 
# Set-WmiNamespaceSecurity.ps1
# Example: Set-WmiNamespaceSecurity root/cimv2 add steve Enable,RemoteAccess
 
Param ( [parameter(Mandatory=$true,Position=0)][string] $namespace,
    [parameter(Mandatory=$true,Position=1)][string] $operation,
    [parameter(Mandatory=$true,Position=2)][string] $account,
    [parameter(Position=3)][string[]] $permissions = $null,
    [bool] $allowInherit = $false,
    [bool] $deny = $false,
    [string] $computerName = ".",
    [System.Management.Automation.PSCredential] $credential = $null)
   
Process {
    $ErrorActionPreference = "Stop"
 
    Function Get-AccessMaskFromPermission($permissions) {
        $WBEM_ENABLE            = 1
                $WBEM_METHOD_EXECUTE = 2
                $WBEM_FULL_WRITE_REP   = 4
                $WBEM_PARTIAL_WRITE_REP              = 8
                $WBEM_WRITE_PROVIDER   = 0x10
                $WBEM_REMOTE_ACCESS    = 0x20
                $WBEM_RIGHT_SUBSCRIBE = 0x40
                $WBEM_RIGHT_PUBLISH      = 0x80
        $READ_CONTROL = 0x20000
        $WRITE_DAC = 0x40000
       
        $WBEM_RIGHTS_FLAGS = $WBEM_ENABLE,$WBEM_METHOD_EXECUTE,$WBEM_FULL_WRITE_REP,`
            $WBEM_PARTIAL_WRITE_REP,$WBEM_WRITE_PROVIDER,$WBEM_REMOTE_ACCESS,`
            $READ_CONTROL,$WRITE_DAC
        $WBEM_RIGHTS_STRINGS = "Enable","MethodExecute","FullWrite","PartialWrite",`
            "ProviderWrite","RemoteAccess","ReadSecurity","WriteSecurity"
 
        $permissionTable = @{}
 
        for ($i = 0; $i -lt $WBEM_RIGHTS_FLAGS.Length; $i++) {
            $permissionTable.Add($WBEM_RIGHTS_STRINGS[$i].ToLower(), $WBEM_RIGHTS_FLAGS[$i])
        }
       
        $accessMask = 0
 
        foreach ($permission in $permissions) {
            if (-not $permissionTable.ContainsKey($permission.ToLower())) {
                throw "Unknown permission: $permission`nValid permissions: $($permissionTable.Keys)"
            }
            $accessMask += $permissionTable[$permission.ToLower()]
        }
       
        $accessMask
    }
 
    if ($PSBoundParameters.ContainsKey("Credential")) {
        $remoteparams = @{ComputerName=$computer;Credential=$credential}
    } else {
        $remoteparams = @{}
    }
       
    $invokeparams = @{Namespace=$namespace;Path="__systemsecurity=@"} + $remoteParams
 
    $output = Invoke-WmiMethod @invokeparams -Name GetSecurityDescriptor
    if ($output.ReturnValue -ne 0) {
        throw "GetSecurityDescriptor failed: $($output.ReturnValue)"
    }
 
    $acl = $output.Descriptor
    $OBJECT_INHERIT_ACE_FLAG = 0x1
    $CONTAINER_INHERIT_ACE_FLAG = 0x2
 
    $computerName = (Get-WmiObject @remoteparams Win32_ComputerSystem).Name
   
    if ($account.Contains('\')) {
        $domainaccount = $account.Split('\')
        $domain = $domainaccount[0]
        if (($domain -eq ".") -or ($domain -eq "BUILTIN")) {
            $domain = $computerName
        }
        $accountname = $domainaccount[1]
    } elseif ($account.Contains('@')) {
        $domainaccount = $account.Split('@')
        $domain = $domainaccount[1].Split('.')[0]
        $accountname = $domainaccount[0]
    } else {
        $domain = $computerName
        $accountname = $account
    }
 
    $getparams = @{Class="Win32_Account";Filter="Domain='$domain' and Name='$accountname'"} + $remoteParams
 
    $win32account = Get-WmiObject @getparams
 
    if ($win32account -eq $null) {
        throw "Account was not found: $account"
    }
 
    switch ($operation) {
        "add" {
            if ($permissions -eq $null) {
                throw "-Permissions must be specified for an add operation"
            }
            $accessMask = Get-AccessMaskFromPermission($permissions)
   
            $ace = (New-Object System.Management.ManagementClass("win32_Ace")).CreateInstance()
            $ace.AccessMask = $accessMask
            if ($allowInherit) {
                $ace.AceFlags = $OBJECT_INHERIT_ACE_FLAG + $CONTAINER_INHERIT_ACE_FLAG
            } else {
                $ace.AceFlags = 0
            }
                       
            $trustee = (New-Object System.Management.ManagementClass("win32_Trustee")).CreateInstance()
            $trustee.SidString = $win32account.Sid
            $ace.Trustee = $trustee
           
            $ACCESS_ALLOWED_ACE_TYPE = 0x0
            $ACCESS_DENIED_ACE_TYPE = 0x1
 
            if ($deny) {
                $ace.AceType = $ACCESS_DENIED_ACE_TYPE
            } else {
                $ace.AceType = $ACCESS_ALLOWED_ACE_TYPE
            }
 
            $acl.DACL += $ace.psobject.immediateBaseObject
        }
       
        "delete" {
            if ($permissions -ne $null) {
                throw "Permissions cannot be specified for a delete operation"
            }
       
            [System.Management.ManagementBaseObject[]]$newDACL = @()
            foreach ($ace in $acl.DACL) {
                if ($ace.Trustee.SidString -ne $win32account.Sid) {
                    $newDACL += $ace.psobject.immediateBaseObject
                }
            }
 
            $acl.DACL = $newDACL.psobject.immediateBaseObject
        }
       
        default {
            throw "Unknown operation: $operation`nAllowed operations: add delete"
        }
    }
 
    $setparams = @{Name="SetSecurityDescriptor";ArgumentList=$acl.psobject.immediateBaseObject} + $invokeParams
 
    $output = Invoke-WmiMethod @setparams
    if ($output.ReturnValue -ne 0) {
        throw "SetSecurityDescriptor failed: $($output.ReturnValue)"
    }
}

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I've run that script before without issue.
What's the exact command are you are running?

subsun and footech:  Thanks both.

The exact command is the last line in the first block in the original question.

I have tried expanding the command to be more explicit using SubSun's notation but it didn't help.  
So it's now:

#WMIMGMT
Write-Host "WMIMGMT Set Namespace Security"
Copy "\\10.0.1.194\c\0 AA Scanner\Scripts\Set-WmiNamespaceSecurity.ps1" "$($Env:Temp)"
pause
Import-Module "$($Env:Temp)\Set-WmiNamespaceSecurity.ps1"
pause
Set-WmiNamespaceSecurity -namespace root/cimv2 -operation add -account steve -permissions Enable,RemoteAccess
pause

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It appears the Copy line of this fails whereas others in the same script pointing to the same folder seem to work.

Here's the error:

Invoke-WmiMethod : Invalid namespace
At C:\Users\adm.NASHVILLE\AppData\Local\Temp\Set-WmiNamespaceSecurity.ps1:63 char:15
+ ...   $output = Invoke-WmiMethod @invokeparams -Name GetSecurityDescripto ...
+                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [Invoke-WmiMethod], ManagementException
    + FullyQualifiedErrorId : InvokeWMIManagementException,Microsoft.PowerShell.Commands.InvokeWmiMethod

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Thank you very much!!