2 years late to the party but this is still a problem when using Notify to add custom watch face so posting this for when this thread shows up in someone's web search.
Export your settings if desired then uninstall and re-install Notify might be required, because I did that, but it didn't seem to do anything.
The solution seems to be plugging the band into the wall. (or usb power from a pc/other low energy decive might work too, didn't try)
If you didn't get to the point of the band saying you must connect to Mi Fit to continue updating (but obviously can't), possibly just adding new watch face while plugged into the wall will fix but I don't know.
Either way, plugging into wall and new watchface, firmware, resources, and font fixed the band and now has all the menus back. If the app says an update completed but the band disagrees, then you need to re-do that update. If you have trouble getting the band to connect, forget and re-pair band both in android settings.
This does assume you have the auth code for Notify to work.