Newer updates for Mac have higher level Security & Privacy settings - this may mean that settings required for Word & Endnote, may be turned off.
Check the Security & Privacy settings.
1. Apple menu - click 'System preferences'.
2. Click 'Security & Privacy' - then click the 'Privacy' tab at the top.
3. Click 'Automation' option on the left.
4. Make sure both the 'Microsoft Word' & 'Endnote' - are both selected / turned on.
With this automation turned off, Cite While You Write function will not work.