Starting Tuesday (July 9), the buttons in my Outlook add-in's dialogs do not fire their callbacks, so no action is taken on click for any user running Outlook 2016 (16.0.4849.1000). Other platforms (OWA, iOS, Android apps) seem unaffected, as well as my Click-to-Run version of Outlook 2016 (16.0.11727.20222).
I know there was recently a vulnerability found with potential conflict and a fix went out for it, but I'm not sure if they're related or which changes I might need to make to my application to resolve this.