I received a reply from Kobo support:
The Kobo Develop Team is working on a better System at the moment and, for this reason, we are facing some different information on the Website.
But if you are still interested in purchasing this book, I will be glad to honor the lowest price for you.
Not sure that it clarifies anything, but at least it sounds like the situation will improve.
thankyou2012 (35% off) - Shows as expired
56b6c435 (35% off) - Shows as not active
56b6c230 (35% off) - Shows as not active