Twitter & Meetup Embed Not Working

Is the Twitter link on it’s own line?

Yes, each URL is on its own line.

Are you able to provide a link?

Does it happen with all plugins deactivated, a default theme?

You can see the URL’s at the bottom of this post:
https://www.texbiker.net/blog/2014/04/16/texas-bicycling-news-and-blog-digest-april-16th/
and also the front page at https://www.texbiker.net/blog

The problem is not present when I use the Twenty Fourteen theme. So My theme Atahualpa 3.7.15 may be the problem. Twenty Thirteen theme works correctly too.

Are you using the visual editor or text? I’m able to reproduce it when I’m using the visual editor and I copy/paste the link.

I use the visual editor.

I tried the text editor and the problem still happens.