The validator experienced some downtown last week. Apologies for that; you should be able to test again.
I’m noticing an invalid value for your twitter:site tag. The value of this optional tag should be a Twitter screen name of your site. And if you use the twitter:creator tag, this is normally the screen name of the author responsible for a post. Therefore, for this specific page, I would suggest setting the twitter:site to “AuthorsWeekly” and not including the twitter:creator tag at all. Let me know if you have any further questions.