Mojave includes new Security & Privacy functions which can prevent EndNote from being able to correctly automate. To correctly set these options...
1) Go into the Apple menu
2) Click System Preferences
3) Click Security & Privacy
4) Click the Privacy tab (along the top)
5) Click the Automation options, along the left.
6) Here, make sure that both "Microsoft Word" and "EndNote X#" are both turned on.
7) Close and restart EndNote and Word.
With this automation turned off, the Cite While You Write functions will not work.