Word could be defaulting to EndNote Online as the Cite While You Write (CWYW) app. You can fix it by changing this preference in Word.
- Open Word and go to the EndNote tab.
- Click Preferences (Near the Help? icon)
- Go to the Application tab in the EndNote Cite While You Write Preferences window. If EndNote Online is selected that is your problem.
- Select EndNote and click OK.
- Test it by trying to insert a citation. If it works, it's fixed.