Sean,
Looks like a bug on our end (mostly). You look to be logged into the admin area of your site using a URL that doesn't have www. However, the front-end of your site has a redirect from the non-www version to the www version. Our Autotune error checker doesn't currently follow redirects.
If you log into your admin area using
www.site.com instead of just site.com, I believe the Autotune error checker should work as expected.
Please let us know how that goes,
Alex