Oh, I thought you were talking about the $5 sign-up promo. My bad.
But it's really irresponsible of Kobo to habitually send out non-working, "already used" coupon codes (is it so hard for their system to verify these codes?) and e-mails about store credits apparently added to but missing in accounts. Such in bad form. There are so many problems, I get confused which ones are being talked about.