Case number missing in email template

Case number missing in email template and my current email template code below any suggestion please.

Hi $user_first_name $user_last_name,

You’ve had an update to your case $acase_name (# $acase_case_number) on $aop_case_updates_date_entered:

$contact_first_name $contact_last_name, said:

$aop_case_updates_description

You may review this Case at: $sugarurl/index.php?module=Cases&action=DetailView&record=$acase_id;