Twitter Image not showing

floating social is not showing the Twitter symbol on articles.
already reinstalled the plugin. any idea what went wrong? am happily using the Plugin on other domains. error occurs only on articles on this Domain:
http://www.viennacitybootcamp.at/fitness-wien/

example:
http://www.viennacitybootcamp.at/fitness-wien/gabi-hiller-o3-wecker-online/
thx!