Including metafields in Request fullfilment notification

Hello, I am having a huge difficulty doing something very simple in Shopify. I am trying to insert 3 meta fields into the request fulfillment notification email. I have read through 10 threads and tried everything. Where am I going wrong? Тhe fields are single line text and they appear as blank in the email.

Разфасовка: {{ product.metafields.custom.product2 }}

Произход: {{ product.metafields.custom.product3 }}

Предназначение: {{ product.metafields.custom.product1 }}