What device are you seeing the issue on and the software version? What version of Office 365 do you have? Do you have any other app like Google that is working?
I have just been told this is a bug and we have pulled this new version of the app from the gallery. We will put the older app back in the gallery
Since they pulled it from the app gallery and yours is unusable as it is, uninstall yours and go to the app gallery, if it is there to install, they already got the old version posted again and you will need to reinstall it fresh. Might as well give it a go now because you will have to eventually, worst case scenario would be that you won't be able to find it yet and won't be able to use the app that doesn't work when you want to.
But I just logged into App Gallery and it is there showing todays date, so it would seem they are done what they needed to do.