Endnote not recognizing previous endnote citations

Alternatively, I would try to convert your endnote citations to unformatted citations in the original document (after accepting the tracked changes) and then compare that document to the document you received back from the editor (after accepting their tracked changes, and who did obviously remove all fields)  - Then you need to go thru and accept the changes the editor made, but not accept any of the citations.  

Probably less tedious than reinserting all the citations.