The hreflang “x-default” attribute worth alerts to Google algorithms the web site doesn’t target any certain language or locale and it is the default web page when no other website page is best suited. Take a look at your Nginx configuration for syntax faults using the command ‘nginx -t‘. If https://addons.prestashop.com/it/seo-indicizzazione-naturale/30904-tag-hreflang-automatici-e-tag-canonici-seo.html