Ok, i got that message error many times too, that problem I fixed it, but i tried many times, make it sure you have the activated option, ok?
and now you just need to add to header.php between the ‘head’ tag in the top this:
<meta name="twitter:description" content="Urban culture, lifestyle">
obviously you change your own description, go to https://cards-dev.twitter.com/validator again and try with a post link, NOT with your home page, this is the way i could get the card but don’t forget that you need to try so many times, sometimes on the validator apparently all is good but when you have to put your email they say you’re whitelisted, and they email you that the card did not validate, but how I said
I clicked the validator so many times with the same way and finally they email me with good news.