Some MP4 files that are created by Final Cut Pro X cannot be played in Windows 8.1, Windows RT 8.1, or Windows Server 2012 R2.
To resolve this issue, install the November 2014 update rollup for Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about software update terminology, see the Description of the standard terminology that is used to describe Microsoft software updates.
The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.