Large Summary Card does not display properly


Hi, I added a Large Summary Card to my blog on Squarespace and run the Card Validator. Blog entries are posted to Twitter and show up there, however, they seem to be collapsed, means they do not show the large visual representation of my original blog entry immediately but only a text and require users to click on a “expand” button at the bottom right corner of the tweet to enlarge and show the visual. I see many other tweets around which show their full visual content without the need to expand and are visually much more attractive (see sample screenshot - the tweet on the top is what I would like to achieve - the tweet at the bottom is how my own entries look like using a Twitter Summary Card with large image). Is there special code I need to use to make my posts as visually attractive?