For one reason or another, you’re not currently charging shipping for a subscription product. Maybe there was no shipping charge when the customer first signed up for the subscription, and you want to start charging for shipping. Maybe the customer qualified for free shipping when they purchased the subscription, but no longer qualify.
The instructions given here involve manually setting a shipping fee that will be added to the subscription total each billing period. Since this is a manual fee, if your shipping costs change in the future, they won’t update here. You’ll have to manually change the shipping costs.