If an additional service (e.g., vectorization or a subsequent design change) was ordered as part of your order, this will be invoiced separately and is due independently of the original order.
If the reminder refers to the main amount of the order, it is possible that the payment method stored with the payment service provider (e.g., with Amazon Pay) was invalid or the debit could not be processed successfully.
Since the delivery has already taken place, the claim remains outstanding in this case and the payment method has been changed to invoice.
The payment status should be checked directly with the respective payment service provider. If the amount was successfully debited there and not refunded, a corresponding proof of payment is required.