The error message indicates that you have selected prepaid balance as your payment method from the Pakettikauppa dashboard, but your account does not have sufficient balance to pay for the delivery. Load money into the account.
If you wish, you can also change your payment method from the “Payment method to be used” menu. The options include saved credit card and monthly invoicing. For activating invoicing, please contact the Pakettikauppa customer service: firstname.lastname@example.org.