This problem can also happen if you’ve had prior versions of EndNote installed on a machine, sometimes the older EndNote CWYW templates will remain loaded in Word. To fix this,
-Open Word, click file/options/addins.
-Where is reads “com addins” at the bottom of the screen hit the drop down and choose “Word addins”.
-If you see mutliple addins in the window, click on each one, the click the delete button. Delete all of them.
Restart Word and test CWYW.