php - Magento 2 offline payment module template issue ← (PHP, HTML)

one text

I have a Magento 2.2.4 store that stopped to send transactional mails caused by this error

Invalid template file: 'Magento_OfflinePayments::info/pdf/purchaseorder.phtml' 
in module: 'Magento_OfflinePayments' block's name: 'info\purchaseorder_ 0'    

My PHP version is 7.1 I copied the moduke module-offline-payments from a local fresh installation and i this doesn't solve the problem

in module-offline-payments/view/adminhtml/templates/info/pdf/purchaseorder.pht
ml

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
/**
 * @var $block \Magento\OfflinePayments\Block\Info\Purchaseorder
 */
?>
<?= $block->escapeHtml(__('Purchase Order Number: %1', $block->getInfo()->getPoNumber())) ?>
{{pdf_row_separator}}

Any idea?