In July of 2018, Create Space closed its store (without telling the authors selling there)
So unfortunately, you can no longer buy the Dead Trees directly from Create Space (not many did) and the old discount codes no longer work.
The discount codes were mainly an offset mechanism for the fact that Create Space charged shipping, and people who weren't in a hurry could save a couple bucks with cheap shipping.
So now, the dead trees are just at Amazon (or you can order from your local bookstore)
However, if you buy the Dead Tree (first) you get the Kindle e-book for free.