I have been having a very similar issue to what I have been reading on these forums since 2013. I am a member of my public library, where I borrow legitimate ebooks to read on my Kobo. ADE seems to have cornered the market for transferring ebooks to Kobos and now they refuse to stand behind their product but refusing to provide help via online chat. I was told I could only receive help on the community pages but the threads I have read do not have any responses from Adobe technical support. They are all people trying to help people but I have yet to find a long-term solution to the issue.
The issue is that when you double-click the acsm file, it does open in ADE and I can read it there. I then drag and drop from Borrowed to my Kobo reader, but that's where the problems start. After undocking my Kobo and waiting for downloads to complete, I cannot open the ebook in my Kobo. I get an error saying that it's not authorized. I have tried what people have suggested, resetting my Kobo, de-authorizing and then re-authorizing the computer and the e-reader but to no avail.
This is it, Adobe. The problem persists and I know it's not with my library or with the files as they work perfectly on my iPad. If you truly DO support your products, now is your chance to prove it. Provide your users with a solution, please.