SSL Certificate Check
Check if a website has IPv4 and IPv6 SSL certificates
Possible reasons the website does not support IPv6 SSL:
1. The server has IPv6 disabled, see Three ways to enable IPv6 on your website
2. The server has IPv6, but the firewall does not allow port 443 (HTTPS) from IPv6 addresses (::/0) open port access
3. The server has IPv6 but no SSL certificate, see Enable IPv6 SSL in Nginx