DMR. ePubs can't be opened.

Question

For many years now I've always had the same Adobe ID. I've had different hardware, replacing stuff that became obsolete or that self-destructed.
All the items in question were purchased by me from the same vendor (ibs.it). However, it's possible they were purchased from from different hardware items (any of two iMacs, a MacBook Pro, and/or one or two different iPads) and/or from two different IBS Italia accounts, without my realizing that a second account in my name had been created. (Yes, I "de-authorized" hardware I no longer owned.)
OK. (a) I'm the same person I've always been. (b) I've always used the very same Adobe ID. (c) I've bought every book being challenged from the same vendor. But now? I've spent a fair amount of money purchasing books I'm not being allowed to read. The vendor tells me this is an Adobe problem. Adobe tells me the company has no answer, so I should consult the forums.
I might be a tad slow on occasion, but I'm not stupid. I'll never again purchase a book subject to Adobe DRM schemes. Still, I'm irritated to think I have to write-off the money I've already spent on books i've legally purchased.

Answer 1

Adobe's implemention of its inept ADEPT DRM mechanism is terrible and extremely customer hostile.
Three suggestions ...  Good luck with at least one of them
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Do you have any devices that still have the correct ID and can still real the book?
If so you may be able to DRM strip your books on that device using a program such as epubee.
You will then be able to read them on any device.
This may be technically against the ts&cs under which the book was sold.
I am not an advocate of DRM stripping to get round reasonable DRM restrictions and to make illegal copies.
However, in cases where the infrastructure of the DRM system fails so badly there is no reasonable objection.
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Books are associated with the ID (remembered by an obsure code called a guid),
and the email address is also associated with the ID.
The book is not directly associated with the email address.
You may be able to get round the problem by
Sign into the adobe website using your email address.
This will presumable access the new incorrectly created second account that does not have any associated books.
Change the email associated with this Adobe ID (see below) to some other email address.
(If you don't have 'spare' email addresses, makey yourself a free one on gmail, yahoo or whatever)
Sign out.
Try again to sign in with your original email address.
With luck, that will be able to give you access again to your original Abobe ID.
To change the email associated with the ID.
Sign in at http://www.adobe.com/ using your old email and Adobe password.
Goto the My Information under your name at the top right  (or https://www.adobe.com/uk/account/account-information.html)
Change the email under Adobe ID near the top left to your new email.
You may need to verify it by clicking on an email that will be sent to the new email.
(I can't quite remember the verification proces, but that's how they usually work).
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If you open a DRM .epub file as a zip, you will find inside a file called rights.xml (probably in a directory META-INF)
Inside that file you will find as string such as <user>urn:uuid:xxxxx-xxxxx-xxxx</user>
where the xxxx pars are your genuine AdobeID.
If you give this ID to Adobe they should be able to recover your access to allow login to the ID.
(If they can't, they are even more incompetent than I think they are.)