twitter card: image no show

Have you submitted your site using the Twitter Card Validator? If not, Twitter won't use your tags to create a preview. It's a very quick process to do so. You just need to get started with the link below:
cards-dev.twitter.com/validator

I hope that helps, but if not, let us know.

Thanks,
Alex

I'm completely unsure what's happening there. I just checked one of your pages for "Malerba", and see that the image is missing in the Validator tool. I don't see any reason why that would be though. Using our own social meta validator tool, the image is fetched properly, which means automated tools work with it. Facebook's own Open Graph debug tool is able to pull the image as well.

The tags inserted into the page also look correct according to their spec:
Invalid consumer key/secret in configuration

It seems that there's something wrong with Twitter pulling the image. I don't know if that's on your server's end or on Twitter's, but I'd suggest trying to look at your server logs when you run a validation to see if the image is being returned properly. If so, all I could recommend is contacting Twitter to see if they can help investigate the issue.

Sorry I don't have a definitive answer, but hopefully that helps you to narrow things down.

Thanks,
Alex