To activate debug mode in Prestashop, you must go to the file manager in Prestashop, enter the config folder and edit the defines.inc.php file:

- define('_PS_MODE_DEV_', false); change it to define('_PS_MODE_DEV_', true);

- @ini_set('display_errors', 'off'); change it to @ini_set('display_errors', 'on');

Note: In Plesk, to access the file manager, we must go to Domains > click on the domain > click on the "Website in" folder: