I've recently had a model rejected where the rejection was later rescinded. Unfortunately I have no way to contact the customer whose order was cancelled to advise them to make a new order.
There are many similar situations where an artist providing files on Shapeways might want to contact a customer regarding an order.
I understand that Shapeways current mode is to keep customer names and emails confidential, so I'd like to suggest a contact means that would not require this:
A simple web form, where the artist can enter the markup invoice number (from the sales report) of a cancelled (or recent, or frozen) order and enter a short message which can then be forwarded to the end customer.
The back-end for this would validate the invoice number against recent orders and the artist's account and retrieve the customer details, or reject the message if it failed validation (not a recent order, order not cancelled or rejected). The message would then be passed to the customer ('the artist XXXX has asked us to contact you regarding order YYYY, with the following message MMMM")
This would allow some degree of artist/customer contact where there currently is none, without affecting customer privacy.