Yep, my latest attempt to take advantage of this offer looks like it is about to fail as well. They sent me an email today saying that the order was delayed, and this is exactly what happened last time shortly before they canceled it. For what it is worth this time I signed up my son for the kids club so as to have obtained access to the code in a legitimate way.
It seem to me that B&N is flat out being deceptive at this point. Though I admit that I have not gone and read through the terms of the kids club and the 30% off offer. Still, their e-commerce store front does allow the code to be applied to Lego items, or at least it did as of a few days ago - I have not tried again since then. I am wondering if trying the sign-up and purchase in an actual brick and mortal B&N store might yield mroe success.