Create new items in a custom list with lookup and Person Field with powershell and CSOM

Hi

I'm trying to create new items based on a CSV - I found some examples with CSOM but I have some errors and I cannot upload this items.

this is the code

$csv = Import-CSV mycsv.csv
$siteUrl = "https://mytenant.sharepoint.com"
$listName = "mylist"
$userName  = "my@tenant.email.address"

$password = Read-Host -Prompt "Enter password" -AsSecureString
$ctx = New-Object Microsoft.SharePoint.Client.ClientContext($siteUrl)
$credentials = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($userName, $password)

$context = New-Object Microsoft.SharePoint.Client.ClientContext($siteUrl)
$context.Credentials = $credentials
[Microsoft.SharePoint.Client.Web]$web = $context.Web
[Microsoft.SharePoint.Client.List]$list = $web.Lists.GetByTitle($listName)


$intIndex = 0;
$addGroup = 0;
write-host "`nImporting data..."
foreach ($row in $csv) {
    [Microsoft.SharePoint.Client.ListItemCreationInformation]$itemCreateInfo = New-Object Microsoft.SharePoint.Client.ListItemCreationInformation;
    [Microsoft.SharePoint.Client.ListItem]$item = $list.AddItem($itemCreateInfo);
    #Customer,StartDate,DueDate,SupportType,AssignedTo,TaskStatus,Title

    $item["Title"] = $row.Title;
    $item["Customer"] = $row.Customer;
    $item["Description"] = $row.TaskStatus;
    $item["AssignedTo"] = $row.AssignedTo;
    $item["Support_x0020_Type"] = $row.SupportType;
    $item["Start_x0020_Date"] = [Datetime]::parse($row.StartDate);
    $item["Due_x0020_Date"] = [Datetime]::parse($row.DueDate);



    $item.Update();
    $addGroup++
    if($addGroup -eq 20)
    {
        $context.ExecuteQuery();
        $addGroup = 0;
    }
    write-host "`r".padleft(40," ") -nonewline
    write-host "Count : $intIndex $row.Title" -nonewline
    $intIndex++
}

Write-Host "Import completed".

When I Ran this, i get the following error:

Exception calling "ExecuteQuery" with "0" argument(s): "Invalid data has been used to update the list item. The field
you are trying to update may be read only."
At C:\scripts\importtable.ps1:61 char:9+         $context.ExecuteQuery();+         ~~~~~~~~~~~~~~~~~~~~~~~+ CategoryInfo          : NotSpecified: (:) [], MethodInvocationException+ FullyQualifiedErrorId : ServerException

After "binging" a lot I suppose there is a problem with lookup field and... i think... with person field (Customer and AssignedTo fields) but I can't find examples that I can understand (the last sentence I wrote was LOAD $,8,1) 

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