Your connection via DDNS displays "Not Secure".

• Make sure that you have registered a valid certificate for your DDNS hostname. For more information on how to create a certificate with the built-in Let's Encrypt service of in DSM, please refer to this article.
• Make sure that you have selected the certificate mentioned above in the system default field at DSM Control Panel > Security > Certificate > Settings (For DSM 7.0 and above) > Configure.