Hello I am using the Plugin RankMath, and they told me that I need to update my Nginx configuration in order to have my Sitemap shown.
Since you are using NGINX, add this code to your NGINX configuration file if your Sitemap pages are not loading or you can ask your hosting support to add it.
# START Nginx Rewrites for Rank Math Sitemaps
rewrite ^/sitemap_index.xml$ /index.php?sitemap=1 last;
rewrite ^/([^/]+?)-sitemap([0-9]+)?.xml$ /index.php?sitemap=$1&sitemap_n=$2 last;
# END Nginx Rewrites for Rank Math Sitemaps