language file .po , it seems not to take in wp directory

I inserted the file woocommerce-orders-tracking-it_IT.po and woocommerce-orders-tracking-it_IT.mo
in
SITE/wp-content/languages/plugins

but it still doesn’t translate in the single order page in my account (the order tab seen by the registered customer)

the word “Tracking number:” and “Carrier:”

other words seem translated. I don’t understand if the link to the file is missing?!