live.ERROR: There are no commands defined in the "cron" namespace

I have been trying to set up crontab on a plesk server with laravel 5.8 , i am getting the following error

live.ERROR: There are no commands defined in the "cron" namespace. {"exception":"[object] (Symfony\Component\Console\Exception\NamespaceNotFoundException(code: 0): There are no commands defined in the \"cron\" namespace. at /var/www/vhosts/****************/httpdocs/vendor/symfony/console/Application.php:585)

I have tried

cd /var/www/vhosts/**********/httpdocs && php artisan schedule:run >> /dev/null 2>&1

 php /var/www/vhosts/**********/httpdocs && php artisan schedule:run >> /dev/null 2>&1

any ideas, thanks

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