Office 365 Update Stopped At 50%

In the Microsoft SCCM Software Center Updates panel, you see Office 365 Update stopped at 50% downloading.
This normally happens when a part of the required update is missing in your Software Update Point.
Take a look in the CAS.log and DataTransferService.log file of the affected client for error codes like 0x80190194 and any .cab files specifically that are failing to download.
This is common in multi-language Office 365 deployments, with each language variant .cab file having an identifying code in the file name.
An example of this is i641028.cab, the update file for one of the Chinese language variants.
When you see a specific .cab file flagged in the DataTransferService.log file check the following:
From the download screen select your Office 365 Client Update Deployment Package.
When you get to the language screen, make sure your changes on the the SUP are present.
Your Deployment Package should be updated on all Distribution Points and clients should update in line with your Software Update policy in the Client Configuration Applet.