Do you use the latest theme and woocommerce versions?
Very likely you just need to synchronize translation files.
Try to update your translation .po file as described here http://betterwp.net/wordpress-tips/create-pot-file-using-poedit./ (the section “Updating a .po (and .mo) file”).
Button Sync (Loco Translate plugin http://xstore.helpscoutdocs.com/article/30-base-theme-translation) allows you to synchronize your translation file with updated pot file. It means if we made any changes in template files that may affect transaltion or we added new string for the translation and you updated theme you need to synchronize your translation with updated files. Only after synchronization, you’ll be able to translate new strings or strings that were changed. You may lose only strings that were changed.
Also, don’t forget to backup all the files before any update.