Unable to log in, gray box displayed instead of realm

When I try to start playing, my realm is not displayed and there is a gray box instead. I have tried reopening the game several times.

 

This has happened before but has always resolved after waiting a minute or two; but it is not resolving this time (waited 10+ minutes so far).

 

I am logged into my Microsoft account; the name and icon are properly displayed on the initial screen.