Oh crap. I still have questions:
if you execute curl -A Twitterbot at the command prompt, does your page still show the twitter:card tags in the section of the page?
How i execute that? Sorry, i don't what that is. I tried in Terminal and gave me a "-bash: syntax error near unexpected token `newline'" message.
is your site accessible by the Twitterbot/1.0 user-agent? Are all the files (including image files) accessible to Twitterbot? you should check http://your-site-url/robots.txt and ensure that it allows access to our crawler.
How can i know that? This is my Robots.txt file: