Shutterfly users - need help!

I have a special offer that I entered in a long time ago for 15 free 4x6 prints.  It ends 8/3, and I ready to "purchase."

But the fine print says I have to enter a code at checkout, but I don't have a code and don't know where to get it.

None of my special offers have a code in my list.

any tips?  TIA