##Variables for Processing
$SiteUrl = "https://lz.sharepoint.com/sites/lz"
$UserName="lz@lz.onmicrosoft.com"
$Password ="****"
$libraryName="DL"

Add-Type -Path "c:Program FilesCommon Filesmicrosoft sharedWeb Server Extensions16ISAPIMicrosoft.SharePoint.Client.dll"
Add-Type -Path "c:Program FilesCommon Filesmicrosoft sharedWeb Server Extensions16ISAPIMicrosoft.SharePoint.Client.Runtime.dll"

#Setup Credentials to connect
$Credentials = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($UserName,(ConvertTo-SecureString $Password -AsPlainText -Force))
#Setup the context
$Ctx = New-Object Microsoft.SharePoint.Client.ClientContext($SiteURL)
$Ctx.Credentials = $Credentials
$Web = $Ctx.web

#Get the List
$List = $Ctx.Web.Lists.GetByTitle($libraryName)
$Ctx.Load($List)
$Ctx.ExecuteQuery()

#Get All List items
$ListItemsCAML = New-Object Microsoft.SharePoint.Client.CamlQuery
$ListItemsCAML.ViewXml = "<View Scope='RecursiveAll'></View>"
$ListItems = $List.GetItems($ListItemsCAML)
$Ctx.Load($ListItems)
$Ctx.ExecuteQuery()

Write-host "Total Items Found:"$List.ItemCount
#Iterate through each item and update
Foreach ($ListItem in $ListItems)
{
    #Set New value for List column
    $ListItem["Archive"] = $false
    $ListItem.Update()
    $Ctx.ExecuteQuery()
}
Write-host "All Items in the Library: $libraryName Updated Successfully!" -ForegroundColor Green