Facebook Comments: facebook url is unreachable

I have the Facebook comments enabled on the site, and I'm having a bizarre issue: when I publish a new post, the Facebook comment section has an error that says the URL is unreachable. If I click on the link it takes me to a Facebook status page where it looks like it's trying to debug the issue...but it says it has a 200 success message and if I go back to the page and click refresh the error goes away.

Any thoughts as to why it's showing this message but after I click on the link it goes away? I think I have my Facebook app settings correct. The domain is just herviewfromhome.com and the Site URL is http://herviewfromhome.com/

Thank you!