I have a nginx server running served through cloudflare.
I get the web server is down (521) error

My nginx config is the following:

conf.d/default.conf:

server {
    listen       80;
    listen   443 ssl;

    server_name  br.myserver.com;

    ssl_certificate      /etc/ssl/certificate.crt;
    ssl_certificate_key  /etc/ssl/private.key;

    #access_log  /var/log/nginx/host.access.log  main;

    location / {
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "Upgrade";
        proxy_set_header Host $host;
        proxy_pass https://0.0.0.0:5173;
    }
}

nginx.conf:

user  nginx;
worker_processes  auto;

error_log  /var/log/nginx/error.log notice;
pid        /var/run/nginx.pid;


events {
    worker_connections  1024;
}


http {
    include       /etc/nginx/mime.types;
    default_type  application/octet-stream;

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    access_log  /var/log/nginx/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    keepalive_timeout  65;

    #gzip  on;

    include /etc/nginx/conf.d/*.conf;
}

This config is the exact same I have on another server working perfectly fine so I thought the problem might come from the cloudflare DNS record which is different but I don’t see anything wrong with it

I know that the dynv6 address works fine because I can connect to the server via ssh with it.
I also know that the app works as intented locally on https://0.0.0.0:5173.

systemctl status nginx
displays the server running fine

journalctl -u nginx.service same

ss -lnpt | grep nginx shows nginx is listening to both http and https requests.

I have also checked with ufw status that the firewall is not blocking those ports.

What am I missing?