BUG prestashop site, error 500

Job ID: 33437461

Budget: €8 – €30 EUR

My ecommerce use Prestashop 1.7.8.5.
When a customer is logging in to the site I get a 500 error. And the site is not more visible.
if I delete cookies the site return visible.
Can be a config file problem?
Related categories: PHP eCommerce Prestashop Symfony PHP