Card validator timeout when trying to test a page on my site


Description of issue:

A couple of years ago I’ve configured my blog (custom engine written in Ruby) to work with Twitter cards. It used to work, however in the last year at least I’ve never managed to get the cards to work. Twitter card validator constantly fails when trying to load a URL from my site, saying:

Unable to render Card preview
ERROR: Failed to fetch page due to: HttpConnectionTimeout

URL affected (must be public):

Troubleshooting steps attempted [note that we will not prioritise posts unless there is evidence of following the troubleshooting guides]:

  • several meta tags with twitter:* are visible in the page source
  • curl -v -A Twitterbot fetches the page just fine, with the same tags
  • says “ is up”
  • says my SSL is “A+”
  • tags are included in the HTML, not added at runtime
  • robots.txt allows all robots
  • I’m not using any CMS, it’s custom Ruby code
  • tested posting to Twitter from a test account, card doesn’t appear
  • ironically, the thumbnail/title/description from the blog post all appear on a card here when composing the forum post…