Hi cala55,
Could you help us confirm some information as below?
1. When did you start the Office 365 upgrade?
2. Have you received the email notification saying the upgrade for Office 365 had already completed?
In our experience, this kind of issue is usually caused by the upgrade for Office 365. Sorry for the inconvenience. We suggest repair the Mac user’s profile in Outlook with the steps in http://support.microsoft.com/kb/2847916 to see if it can work.
Any updates will be appreciated.
Thanks,
Lee Li