I just tried again and got the same error a day after:
It has come to our attention that your order CAD-C2411173 cannot be completed because the source files for the project “Points of Light” contain errors preventing it from being printed. We've unfortunately had no choice but to remove this item from your order, and have refunded you accordingly. You should see a refund reflected in your original payment method within the next few business days.
We'll also be contacting the author to make them aware of the problem, but we do apologize for any inconvenience that this may create.