I have my woocommerce with WPML plugin. Which allows for multilanguage sites. Your plugin claims to be compatible with WPML. But when I set a coupon with a free product. It will always add the product in the same language, instead of showing the corresponding other language version.
I.e I set up a coupon with a free product (I search the product and I select the english version for instance in the admin setup).
then when I use the coupon, it works, it adds the product in english. But when I go on the french version of my website, I use the coupon but it will still add the englisch product instead of the french translation.