Over the past 2 days, I have come across 3 DRM'ed books that can not be dowloaded as epub via ADE. ADE chokes on the epub download URL, and when I try that URL on a web browser, it is, indeed 404.
I tried reporting this to Kobo, and got a credit for one of the books, but I don't think the issue got passed on or reported to anyone who would be able to solve this kind of problem. After a bit of experimentation, I found a Free book that replicates the issue.
https://www.kobo.com/ca/en/ebook/enough-40
I would be interested if anyone else is able to try to download this EPUB and see if it's unique to my accoun or a recent failure of Kobo server. (I do not know if the resource UUID in the ACSM file is unique per user, and we all get a unique epub, or if it's the same encrypted epub everyone gets.