Why is this custom backstage UI for Word not displaying its user interface?
This is a bug with Office. I can confirm in my environment, this worked again after updating Word manually with the November 8 update which came out yesterday. This update did not show up when I tried to search for updates in Windows 10, instead I had to install it this way:
Inside of Word, click File to open the backstage.
Click on the Update Options drop-down.
Select Update Now.
Once you update to Office version 1610, build 7466.2038, this bug goes away:
