Twitter Card Summary_Card_Large not showing image in front of the tweet (only in details)



I successfully registered for the twitter card.

In the validator, the card is shown properly:

The picture is visible only if a user click on the “View Summary” button:

But the picture is not shown on the tweet in the front-end page of the twitter account,
while other services properly show the image in front (see other tweets send from our mobile app, displyaing a screenshot of the mobile app).

What is wrong in the configuration we use to prevent the image be shown on the tweet?
We need images to be shown in front of the tweet, not the detailed view: that’s the purpose of twitter card.

We are looking forward to release the website, could you review it ASAP please?

Thank you,
Luigi / CEO - XDiscovery