Does not tweet the card


I have added the metatags in the page, validate the tags and activated the card with Twitter. Then I tried to tweet one of my posts and it just tweet with no card.
I even added another button to test it, but nothing.
My blog is O (a)Variado and the post I tried was O Didgeridoo (parte 1)

what could the problem be???
thanks for the time spent.