As always, Kobo codes don't work on books published by big name publishers: Hachette, Simon & Schuster, Random House, HarperCollins, etc. So if you see one of these as the publisher for the book you're interested in, you can save yourself the hassle of even trying the code

. Not that it's all that hard to try it...
The codes do work on many (but not all) smaller/indie publishers, as well as most self-published books, and I've already used the Partners22 code on several of those.
And they also often (but again, not always) will work on older backlist by established authors, when those authors have gotten the electronic rights for their early books, and republish those books themselves, or with the help of one of the presses that specialize in helping authors do that.
So, I'd far rather have the coupon than not!
Also note that which publishers the codes will and won't work on can vary slightly by country.