When you install Microsoft Exchange Server 2013 on a Window Server 2012 R2-based computer, default apps (such as Bing map and Action item) in Outlook Web App do not work.
This issue occurs because the logic to load app resources is broken in Windows Server 2012 R2.
To resolve this issue, install the following update:
2936880 Cumulative Update 5 for Exchange Server 2013
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.