mkork

Solution found. In case this helps anyone.
I am using the Greek localisation. Which means the greek iso is “el”. Woo commerce files are like this “woocommerce-el_GR.mo”, which means they have the “el_GR” and not “el” extension. Rename this to just “el” and it will work. Oh, don’t forget, the correct path in wordpress 4.0.x is “wp-content/languages/plugins/”. So the file has the path “wp-content/languages/plugins/woocommerce-el.mo”.