In the following blog, I am going help you verify that WAC Server is working via circumventing a WOPI Host (IE ruling SharePoint as the potential culprit). This is helpful when you want to test Office Web Apps viewing capability independent of SharePoint, Exchange or Lync.
1. By default the Office Web Apps new farm configuration does not set OpenFromURLEnabled to True. Set to True by running the command below in Powershell on the WAC Server.
2. Add a workbook to a folder (and then Share that folder) on the WAC Server.
Example: Create a folder called "Test" on the root of C: (C:\Test\Test1.xlsx)
Share the folder with Everyone.
If this location is on another Server (Not the WAC Server), you need to Share this folder with the WAC Server (the Computer Account (follow below screenshot on how to do this)).
After you have chosen Computers, you need to WAC Server name > Check Names (make sure it resolves) > OK
3. We now need to generate a http:// URL to that folder. Open IE and browse to http://<ServerName>/op/generate.aspx
Use the URL that is next to "InternalURL" when you perform Get-OfficeWebAppsFarm
If you are not using an "InternalURL" then you will obviously have to use "ExternalURL"
In the below example the URL is: http://wacserver/op/generate.aspx
4. Enter the UNC location of the workbook. \\<Servername>\test\test1.xlsx
In the below example the UNC location is \\wacserver\test\test1.xlsx
5. Click " Create Link " and then click "Test this link."
If this works, then you know the WAC Server can render the workbook and something else is configured incorrectly.
If this fails, you may want to considered quickly rebuilding your WAC Server the below blog:
NOTE: This testing feature does not currently work with Windows Server 2012 R2. Our product team has been notified.
Office Web Apps 2013 - Rebuild your Farm in a few Easy Steps! http://blogs.technet.com/b/office_web_apps_server_2013_support_blog/archive/2013/12/20/office-web-apps-2013-rebuild-your-farm-in-a-few-easy-steps.aspx
Any word on Office Web Apps Server compatibility with Windows Server 2012 R2?