March 2016 Update:
We have re-enabled Dropbox Integration:
Enable third-party storage in Office 365
User goes out to http://office.com and signs in with an Office 365 Account. User selects one of the office apps links on the page. The office app will try to launch in the browser and save a document into the user's OneDrive for Business site.
The user will get an error message: Sorry, we couldn't create your new document
The Go to OneDrive for Business link in the error will redirect the user to their OneDrive for Business site. If the user clicks Try again they will be presented with the Office App template picker and will ultimately end up back at the same error message. If the user browses directly to their OneDrive for Business site and selects New -> Document, they will be able to create a new document. The user will also be able to open existing documents in the Office Apps from the Office.com site.
In November Allow people to use third-party hosted storage services was added to Office 365 to disable Dropbox integration. When the Dropbox Integration is disabled in the Office Portal, this also causes the users to not be able to save new documents to their OneDrive For Business sites. Additionally it is breaking the Office Apps integration with Skype for Business.
The Tenant Admin needs to go to portal.office.com and enable the integration in order to restore functionality.
Service Settings -> Office Online
Set Allow people to use third-party hosted storage services to ON
Wait a few minutes for the settings to propagate and then the users should be able to save documents again.
The Office Apps team has temporarily disabled Dropbox integration in the service.
Add Dropbox to Office Online
This will prevent customers that don’t want to see Dropbox from seeing Dropbox in the UI when the Tenant Admin enables the integration. A fix is in the works to enable Dropbox integration and give tenants the ability to disable the integration from https://portal.office.com. I will update this blog when I have an update.