Going by the posts in this thread, I think Kobo has an unacceptably high rate of undownloadable books. I got two during the sale, also, and I've also bumped into this issue more than once in the past.
I've reported one and I assume I'll get a refund. I'm trying to decide what to do about the other, which is on my "offshore" account. Do I want to invite the scrutiny (as if Kobo scrutinizes!
)? Obviously, given the sale, it's for a trivial sum. I'll probably let it go.