Hello Chris,
Actually, there has been a planned SharePoint Online upgrade to Office 365 recently.
You might try creating a new site and a new library to see if it works.
In addition, I would recommend you check the Service Health and Planned maintenance from the Admin page of your Office 365 Portal. See if any related information is available there.
For your reference:
Update to Office Web Apps with SharePoint SU4
Regards,
Cherry Wang