Do you have:
- A virtual server listener configured for the
www.domain.com
domain as well? - A corresponding SAN in your cert that covers
www.domain.com
For your error, it's probably the first one. When the traffic comes in under www.domain.com
, there's no virtual server configured to listen on that hostname and it's likely falling back to a default response.
Not sure how that works with Github pages, but in general, that's usually what it is.