Error "Not Implemented" when running "Update Citations and Bibliography" command

I am receiving the error “Not Implemented” when running “Update Citations and Bibliography” command. I pasted unformatted citations following this method: Ctrl-C with the target reference in EndNote 21 selected and Ctrl-V in MS Word O365 desktop.
I dismiss the error message and the “Update Citations and Bibliography” command seems to have completed successfully with no further error messages displayed.