This flash plugin was blocked because it is out of date
Solution 1:
Google Chrome will always block older versions of Flash. I think you might be better off either using another browser or an updated version of flash, because Chrome is not going to play nicely with old flash no matter what you do.
Solution 2:
Chrome seemed to use an outdated version located in /usr/lib/mozilla/plugins, so finally this works for me:
sudo rm /usr/lib/mozilla/plugins/libflashplayer.so
sudo apt-get install adobe-flash-properties-gtk adobe-flashplugin