Books no longer show up in my Digital Editions library?

I am so tired of this problem that I just paid $5 for Bluefire reader (on mac osx), which is on top of the cost of my Adobe account. I do not like Bluefire’s interface at all (no thumbnails, extremely poor organization capabilities) but at least it shows my books after I had to upload them one by one. It sucks but it sure beats coming back to Adobe Digital Editions for an hour every few weeks to try to fix this issue. So many hours lost to this problem, I just decided to abort mission and switch to a substandard but at least reliable app. Shame on you, Adobe. It’s about time you pay attention to this product.

Same problem. When my Windows 10 crashed and everything had to be reinstalled, the library wouldn't show. I found that I had to delete the original My Digital Edition folder that I had transferred in before ADE would read the My Digital Edition.old folder. Now everything is good again - for the moment at least.

I just want to add my voice to the others. I had a library of over 200 books vanish. Renaming the folders only seemed to make the new books appear, but did not restore the years of previous purchases. I can't even find the original epub files anymore. Not sure what has happened, but I'm not happy with the product.

Hi, I am having the same issue. Open ADE and the library that I can clearly see in my documents folder is not visible. I have been using this program for years and no issues until a few months ago. I am looking for Adobe to supply a permanent solution for this issue, not a work around users need to keep doing every few weeks. As this is the only way many libraries allow you to access their Overdrive ebooks and Adobe has a monopoly in this space I would expect some support for what is clearly their program.

I have seen this response so many times and tried it, but it doesn't work.  There must be some other way to retrieve previously purchased books

Thank you so much, I've been searching forums for a week trying to find an answer - this finally worked! 

Opened ADE library today, October 7, 2019 only to find the 433+ books in my library gone.  Would really, really like to know why this has occured and how to fix the problem while retrieving my full library.

BTW: I am running Windows 10, tried the renaming of the folder as posted by Nanaky and zilch happens - no books.  From the responses below those of us running Win 10 still do not have a solution.

This problem hasn't been solved.

Does not work. I own a phone and a tablet, both Android 7.0, and both have Adobe Digital Editions installed. I can only access my synchronised contents via PC.

I'm experiencing the same problem as you did, but with Windows 10.  It worked perfectly after installing the update a few days ago, but now nothing populates in my Library.  I tried the fix that worked for you, but no change -- still an "empty" Library, although there should be several ebooks in it.  Can anyone suggest other things to try?