I was able to use the coupon too, without any hassle. It felt a bit like the old days, and Kobo got more money out of me than they have in quite a while.
I picked up several boxed sets/omnibuses/collections - with the 60% coupon added on top of the savings that are usually (although not always) built into the price of box sets, I was able to get a bunch of books quite inexpensively!

(and karma) to the OP!!!
P.S. If you want to try this coupon out on some boxed sets, there is a thread that is sporadically updated with lots of info on boxed sets, precisely for potential use with high-value Kobo coupons. Many of the box sets are only available abroad (i.e. not US, usually not UK). See this link:
https://www.mobileread.com/forums/sh...d.php?t=228358