Hello,
I read this in woothemes :
Making your Localization upgrade safe :
If you keep your custom translations in woocommerce/i18n/languages (WooCommerce < 2.2+) they can be lost when upgrading. To make them upgrade safe, instead place them in wp-content/languages/woocommerce/. All translations will be automatically added to wp-content/languages/woocommerce/ with WooCommerce 2.2+.
https://docs.woothemes.com/document/woocommerce-localization/
LoCo uses the url wp-content/languages/plugins/ and woocommerce/i18n/languages but not wp-content/languages/woocommerce/. I think that’s issue ??