I want to urge anyone who is considering upgrading to OS Sierra and who uses Endnote NOT TO UPGRADE. I upgraded and spent a weekend playing around with different versions of Word 2011, 2016 and two macs - I can conclude that Endnote CWYW plug in is not compatible with OS Sierra and thus I would urge anyone considering upgrading to wait until X8 is released. I downgraded to El Capitan and eventually Endnote is working again with Word 2016.
The cite whilst you write plug in is essential for most users and hence latest Endnote is not compatible in anyway with Word 2016 when the OS is the new Sierra.