Using PnP PowerShell to attach a file to an item

Try this script

function writeItem(
$itemTitle,
$itemOther,
$attachments
) {
# check if file exists first
$items=Add-PnPListItem -List testlist

$newListItem = Set-PnPListItem -Identity $Items.Id -List testlist -Values @{"Title" = $itemTitle; "other" = $itemOther}


for ($a=0; $a -lt $attachments.length; $a++) {
#Write-host " " $attachments[$a]
writeAttachment -item $items -fileWithPath  $attachments[$a]
}

}

function writeAttachment($item, $fileWithPath)
{

$ctx=Get-PnPContext
$memoryStream = New-Object IO.FileStream($fileWithPath,[System.IO.FileMode]::Open)
$fileName = Split-Path $fileWithPath -Leaf
$attachInfo = New-Object -TypeName Microsoft.SharePoint.Client.AttachmentCreationInformation
$attachInfo.FileName = $fileName
$attachInfo.ContentStream = $memoryStream
$attFile = $item.attachmentFiles.add($attachInfo)
$ctx.load($attFile)
$ctx.ExecuteQuery()
}

Connect-PnPOnline -url https://tenantname.sharepoint.com/sites/contosobeta

$Att=@("C:\copyfile.csv","C:\AllSubsitegrouppermission.csv","C:\AllUserWithLicenseType.csv")

writeItem -itemTitle "test6789" -itemOther "efgh" -attachments $Att