@odedtalmon, as the string is working on our end, hence this is not a plugin related issue.
The translation will only work if this is saved in a database. So, please do create a vendor account using our email firstname.lastname@example.org and share temporary admin access.
I see, this gave me an idea that I would like to try before giving you access to check.
There is the same issue with Woocommerce and wp-admin language, if my user’s language is set to English I will receive Woocommerce emails in English, if it’s set to Hebrew then the emails would arrive in Hebrew. Perhaps if I set the Vendor’s language to Hebrew the translation would then work.