This was reported a few days ago, but I only just installed the MacOS update myself to check.
The Inform IDE has a serious bug under MacOS 10.12: the “Story” pane just doesn’t display anything. The game compiles correctly but won’t run in the IDE.
This is a general CocoaGlk bug – all versions of Inform 7 have the same problem (going back to 6G60 at least). So does Zoom.
This is particularly bad timing with IFComp coming up. If you’re scurrying to finish your IFComp entry, you really don’t want to upgrade MacOS and find your development workflow has run into the curb. So be aware.
(It is possible to compile, copy the game out of the project file, and test it in another interpreter. The debug-mode game file is at project.inform/Build/output.ulx after compilation.)
Bug filed: inform7.com/mantis/view.php?id=1953