Hi there @cantabro - appreciate you indicating that nothing has changed on your side, but I just went through our troubleshooting steps from the pinned post, and I think something must have changed somewhere...
The Tweet you referenced links to http://jussemper.org/index.html#.WNbIB7iA4Kc.twitter
The markup in that page contains a reference to this image http://jussemper.org/Resources/entender%2Bdecrecimiento.png
When I attempt to fetch that image using our crawler's user-agent, I get a Forbidden response:
$ curl -A Twitterbot http://jussemper.org/Resources/entender%2Bdecrecimiento.png
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<p>You don't have permission to access /Resources/entender+decrecimiento.png
on this server.<br />
<p>Additionally, a 403 Forbidden
error was encountered while trying to use an ErrorDocument to handle the request.</p>
So it looks like something on the server - possibly the
.htaccess file, or your host's configuration - is blocking Twitterbot from fetching your images for display. I'll also note that the same URL to the image also returns 403 even to my Chrome browser.