Task list - setting EnableAssignToEmail using PnP powershell - not working consistently

Try the below script.

$csvFile = ".\SiteIDs.csv"
$sites = Import-Csv $csvfile
$cred=Get-Credential

foreach ($site in $sites)
{
Connect-PnPOnline -Url $site.URl -Credentials $cred
$ctx=Get-PnPContext
$List = Get-PnPList -Identity Tasks
$list.EnableAssignToEmail = $true
$list.Update()
$ctx.load($list)      
$ctx.executeQuery() 
}