Cannot request subdomain through HTTPS

I created a subdomain for a site by adding a custom DNS A record and set it to our EC2 instace's public IP. We are able to make requests through HTTP but HTTPS requests fail. Aren't subdomains given SSL certificates automatically? Its been almost 24 hours since I created the subdomain. I know it could take around 24-72 hours but I just want to know if I'm doing anything wrong.

Thanks in advance.