Nginx – HTTPS/SSL Response gets blocked, HTTP Response works fine

My Website http://bavarian-joke-generator.org is running. Sadly I was not able to get the HTTPS version working because I have been encountering the following problem since enabling it via a certificate by letsencrypt.org via Certbot:

The Response from my server seems to either get blocked or intercepted somehow

• Firefox:
  

• Safari:
  

My Question is:

What am I missing here? I’ll list the following things already and really seem to be out of resources on what the issue can be caused by.

Details:

As seen from the NGINX logs below, the response is successfully sent by my Nginx container.

• HTTPS Response that ends up getting blocked:
  
• HTTP Response that works as expected:
  

The Server is provided by Hetzner and the following UFW Firewall settings are active (blocked IP address is not mine):

The whole code can be seen on its GitHub repository

But I specifically want to mention the NGINX config used. Also note, that NGINX is running as a container as part of ad docker-compose file:

• Config:

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;
    proxy_max_temp_file_size 0;

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

• Template included above

server {
    server_name bavarian-joke-generator.org www.bavarian-joke-generator.org;
    listen 443 ssl http2;
    listen [::]:443 ssl http2;
    ssl_certificate /etc/nginx/ssl/live/bavarian-joke-generator.org/fullchain.pem;
    ssl_certificate_key /etc/nginx/ssl/live/bavarian-joke-generator.org/privkey.pem;
    listen 80;
    listen [::]:80;
    add_header Strict-Transport-Security 'max-age=63072000; includeSubDomains; preload' always;

    add_header Content_Security-Policy "default-src 'self'; script-src 'sha384-7FvcOpf85HsGS89sLrvOOHZYqgaEqbfUi87HhpbqbndTSFw+XpzbDMK5ZcxD28fe'; frame-ancestors: 'self'; form-action 'self'; base-uri 'self';";
    add_header X-Content-Type-Options: "nosniff";
    root /usr/share/nginx/html;
    error_page 400 /errors/400_wrong_input.html;
    error_page 404 /errors/404_joke_not_found.html;

    location / {
    }

    # SSL Certificate:
    location /.well-known/acme-challenge/ {
        root /var/www/certbot;
    }

    location /errors/ {
        root /usr/share/nginx/html;
        internal;
    }

    location ^~ /assets/ {
        root /usr/share/nginx;
    }

    location ^~ /RegEx/ {
        root /usr/share/nginx;
    }

    location ^~ /ssr/ {
        # pass will exchange ssr/ for /:
        proxy_pass "http://${SSR_HOST}:${SSR_PORT}/";
        proxy_http_version 1.1;
        proxy_set_header   "Connection" "";
        proxy_intercept_errors on;
    }

    location ^~ /auth/ {
        # pass will exchange auth/ for /:
        proxy_pass "http://${AUTH_HOST}:${AUTH_PORT}/";
        proxy_http_version 1.1;
        proxy_set_header   "Connection" "";
        # No error pages -> Do not intercept errors
    }

    location ~ .(?:js|.css)$ {
        root /usr/share/nginx/html;
    }
}

I already tried:

• splitting the NGINX server block into two that listen on port 80 and one on 443 separately and redirecting to HTTPS block
• enabling ufw rules again
• renewing my ssl certificate
• checking if my ssl certificate can be found via sslhoper.com
• checking if any other firewalls exist and are blocking