I'm a developer at Zotero. For at least a year now we've been getting Mac Word 2016 reports about our plugin tab not appearing. The macros appear in the Macros menu and function fine, but the tab won't appear. The plugin is a .dotm template. We've guided our users to various troubleshooting steps, including resetting the normal template, but nothing seems to help, aside from installing the older template we use for older versions of word. (While working on the updated .dotm template we've had this bug the other way around too - tab not appearing for users with the .dot template, but appearing with the .dotm one)
It doesn't help that there doesn't seem to be any way to reproduce this, but it certainly only affects Mac Word 2016 users. Older versions are fine, Windows versions are fine. I'm not sure where the best place to talk about this is, so if it isn't here, please point me in the right direction.