This error message refers to an internal EndNote error and could be the result of several things. So, these steps may not correct your specific issue. These are merely the most common causes of this problem and may resolve it on your machine with EndNote.
The error -1712 is essentially an AppleEvent timeout error. If you haven't restarted your computer in a very long time, a restart will frequently resolves this issue.
The error -1712 can also be caused by running an ‘overabundance’ of processes at the same time. Close/exit other apps on your computer!
For more Macintosh Error codes:
https://krypted.com/lists/comprehensive-list-of-mac-os-x-error-codes/
Please read this comprehensive article about error -1712 at Clarivate EndNote knowledge base:
https://support.clarivate.com/Endnote/s/article/EndNote-Mac-EndNote-is-not-responding-Error-1712?language=en_US