"This library is currently being used by someone else. Try opening it again later"

Greetings All,

I too experienced this frightening issue with Endnote X8. I called Endnote support (1-800-336-4474; Option 4) and they wonderfully gave me the following instructions for MAC Book Pro (High Sierra):

  1. Create a new folder in APPLICATIONS called “Endnote Libraries”.
  2. Copy and paste your corrupted Endnote library (.enl) and its corresponding .Data folder to the new folder you just created. 
  3. Open Endnote X8 program.
  4. Go to Tools “Recover Library”.
  5. Choose the new copied version of your .enl file in the “Endnote Libraries” folder you just created.
  6. It will recover your library and make a new file with a new name by simply adding “-Saved” to it (ORIGINALNAME-Saved.enl) and it will also paste a new corresponding .Data folder with the “-Saved” added.
  7. Open the new “-Saved.enl” file and voila - your library is back.

All of my groups, attachments (PDFs,), etc. were there too. Crisis averted