Meta UI can vary by country/account type. The key is: start from SendZen View Status → open Business Manager → navigate to Payments/Billing.
Note: Billing updates can sometimes take time to reflect because Meta systems update asynchronously. Wait, refresh, and re-check.
Note: Billing and payment setup is controlled by Meta. Sometimes after adding a payment method (and tax info), it takes time for Meta to approve/activate it. If billing status doesn’t update immediately, wait and refresh — timing depends on Meta.