This has nothing to do with the version of endnote, but with what you have set as your own “temporary delimiters” which should be set to curly brackets.
I would first make a copy of the document (so you have something to go back to) and then open the bibliography menu and change them to curly brackets (better yet, to change them in the preferences section). I suspect if yours are already formated they will be converted to curly, and the curly bracketed ones will be formated assuming they are in an accessible library. Yours should be curly. It complicates the use of endnote if you try to use normal parentheses, as it will be trying to convert every parenthetical statement to an endnote citation.
the images for these settings (windows version) are attached. (preferences is found under Endnote’s edit menu >preferences in the second snip.)
