SSL issues with DDNS (Dynamic DNS) often happen because SSL certificates are domain-specific and DDNS hostnames can change IPs frequently. If you’re using a free DDNS service, browsers may not trust the SSL certificate or it might not match the hostname. To fix this, use a trusted SSL provider that supports your DDNS domain, or consider using a static IP with a proper domain. Also, make sure your router or device supports installing a valid certificate.