Tweets not appearing as a Twitter Cards
Are Twitter Cards implemented on the website link you're Tweeting?
Twitter Cards would need to be directly implemented by the website owners within the HTML. If you're sharing a link to a website where Twitter Cards have been implemented, then this should work great once your Tweet has been published. However, if you're sharing a link to a website where Twitter Cards have not been implemented, unfortunately this wouldn’t work.
If you’re trying to determine if the link you’re sharing is set up to use Twitter Cards, jump over to Twitter’s Card Validator tool here. You’ll be able to enter a URL to preview how the card might appear on Twitter’s feed. If no preview pops up, then unfortunately Twitter Cards have not been implemented on the website link you're sharing and therefore it wouldn't be possible to make thee Tweets appear as Cards on your feed.
Did you choose an image to go with your Tweet?
Twitter works a little differently than Facebook, LinkedIn and Google+, in that a link preview is not generated while you’re composing a post. That said, the Twitter Card would be generated once the Tweet has been posted. We’re sorry we can’t give you a more immediate display of how this may appear once it’s been posted; it’s something we’d love to be able to do in the future.
If that doesn’t do the trick, please get in touch so we can take a peek at your posts and find out what’s going on!