All in One SEO plugin stopped working after update

I'm using the "All in One SEO" plugin. I never had issues with it. It worked perfectly fine. Recently, however, I noticed that it doesn't generate the information (title, description) anymore.

Especially the SEO-friendly description I enter in my posts in the field that the plugin provides is totally being ignored by search engines, Facebook, Google+. Instead just the first few sentences of each post appear.

As I haven't changed any settings recently, but remember that I automatically updated Wordpress to the newest version as well as a few plugins, I suppose it has something to do with that. I'm quite sure that "All in One SEO" was one of the plugins I updated. The newest version came out in late December.

I checked the plugin's settings and everything seems to be fine.

I searched for similar issues everywhere, but couldn't find anybody with the same problem. I'm not sure how to fix this.

If the plugin is causing the issue, then I don't know how to fix it as the settings look perfectly fine to me. If it's not the plugin, I have no idea what else could cause it.

For reference: my blog

Thanks for any advice you can give me! :)