I was having an issue when trying to access my blog through the www subdomain, but I managed to fix it! The issue was roughly as described in the title, I was able to access superfluoussextant.com, but I was unable to access www.superfluoussextant.com. I decided to make a blog post every time I find an issue that I couldn't solve trivially through googling, here goes the first one.
Here is a list of relevant technologies I'm using to bring this blog to you:
I have set up a github repo with a project page by creating a gh-pages branch, setting the custom domain, and creating a CNAME file with the following contents:
I had also set up the following custom resource records through google's DNS settings
Although I could reach my blog through the apex domain superfluoussextant.com, I couldn't reach it through the www subdomain www.superfluoussextant.com. The error I saw was dns_unresolved_hostname, you can see how it expressed itself in the image below (actual manifestation depends on DNS).
I had been following the excellent tutorial by Curtis Larson, but there was a difference between his tutorial and what I wanted to do: he was using a custom domain for a user github page while I was trying to use a custom domain with a project page. (I thought) the only difference between the two was the default url where they are served by github pages. By default user pages are served at user.github.io while project pages are served at user.github.io/projectName.
Because I was publishing a project page, I strayed from the tutorial by setting my CNAME record to jchapman.github.io/superfluoussextant, however this was not correct. Even though I was trying to publish a project page instead of a user page, I still needed to make the CNAME record point to jchapman.github.io. The correct records are below, the changed one is highlighted.
If you're having a similar issue, all you have to do is make sure that your CNAME record points to username.github.io even if you are trying to publish a project page with a custom domain. Also remember that it takes some time for DNS record changes, for me it was at least an hour.
Please let me know if this helped you by commenting below!