I was prompted by Office 365 to change my password, and I did so late yesterday. This morning, the Outlook 2013 desktop client would not connect to Exchange at all (would not pull down new messages or send messages in my outbox).
I tried a few troubleshooting steps including running a Repair on the Exchange account via Control Panel/Mail. That apparently fixed the outgoing mail problem -- but Outlook still cannot pull down new messages and repeatedly puts itself in "Working Offline" mode.
Ridiculous, but par for the Office 365 course. I mean, if you're going to force users to change their passwords periodically, shouldn't your system be equipped to seamlessly handle such changes?