Where is your field located?
Options will work with parameter ‘option’,
if its Product/Page specific you need Prduct/Page ID then use ID as parameter,
also have in mind that WooCommerce could have more that one notification (Cancel, Pending, Complete order…)
Get value from another post or Get value from Options page
From WooCommerce website:
Woocommerce how to customize emails in WooCommerce
