The problem: Unable to translate strings, the translation was missing from the .mo/.po file.
The solution: Go to WPML >> Theme and plugin localization and select "Translate by WPML". After that scroll down and find the plugin WooCommerce and select it. Scroll down to the bottom of the page and press the button "Scan the selected plugin for strings". After the scan completes you can go to WPML >> String translation and find and translate the strings. More information can be found in our documentation here: http://wpml.org/documentation/getting-started-guide/string-translation/
