Your custom domain's TLS certificate is valid and traffic is routing correctly through our edge, so the SSL setup on our side is working as expected. A "Not Secure" warning with a valid certificate is typically caused by mixed content in your site (images, scripts, or stylesheets loaded over http:// instead of https://), or by your browser caching an earlier insecure response. Try opening the site in an incognito/private window, and check your browser's developer console for mixed-content warnings.