I have a custom domain setup to use Netlify as the DNS provider. While the root of the domain hosts a site, I setup a CNAME record on a subdomain to alias to another site. I can access both the site hosted at the domain root and the site the CNAME record points to via https no problem. However, when I try to access the other site via my subdomain, browsers get upset about cert errors:
The settings for the site hosted at the domain root shows that HTTPS is enabled, though I configured the CNAME record in the “Domains” settings, rather than the “Site > Domain” settings and there doesn’t appear to be anyway to see cert related stuff in the former.