User changed the Payment Term in Settings > Billing & Invoices > Accounts Receivable, but the change does not reflect on invoices.
This happens because changing the Payment Term in Settings only affects new projects and not existing ones. You should update the Payment Term at the project level in Projects > General > Billing Options under Terms & Currency in order to reflect it on the project invoices. You can also make a Batch Change to edit the payment terms for all or selected projects (Actions menu). Check out this article for more: Message at the bottom of invoices.
Note: Updating the payment terms at the project level only affects new invoices of that project. You cannot update it for its existing finalized invoices. However, you have the option to convert those invoices to draft and then update the Billing Term field in the invoice details (only for batch invoices). Manual Invoices in draft mode take their payment terms from the project level settings when finalized.