Not a Valid Facebook URL

I'm trying to help out a buddy and get the Facebook Page Plugin happening on his website. I've done this before, but I keep getting an error that says, "Not a valid Facebook URL."

The page is https://www.facebook.com/ustaekwon. It's obviously a page, but what is it that would prevent it from being registered as part of the Page Plugin?

This is the interface I'm using: https://developers.facebook.com/docs/plugins/page-plugin

Any help would be greatly appreciated.

Thanks!