The Autotune Error Check tool scans the HTML output for your home page. When I try to visit the page you're running the Error Check tool on, it doesn't load. In that case, the Error Check tool won't be able to load it either and run it's scans.
If you have the site enabled for only certain IP addresses or other protections to prevent anyone from seeing it, that would explain the problem. I'd recommend testing JFBConnect's authentication or other features to see if you're having an issue or not. The Error Check tool tries to point out possible issues, but it's not necessary to run.
The other alternative is to make your site publicly available, briefly, so that the Error Check tool can fetch the home page and run its checks.
I hope that helps,
Alex