Setting up a new Office Web Apps Server 2013 farm we ran into an odd error that was the result of a bad configuration setting on the farm.

Since the load balanced DNS was not yet configured we decided to setup a single server as if it was a test environment (using http as opposed to https as the cert is for the load balanced URL).  Following the base instructions we ran the New-OfficeWebAppsFarm command and the farm configured.  We then went to the http://wavservername/hosting/discovery URL and it said that it had everything working.

We then configured SharePoint to link to the WAC farm by using the New-SWOPIBinding command.

At this point the SharePoint farm would display the Office Web Preiview, but we would get a "Sorry Something Went Wrong" message that was similar to this:

Sorry, Somethign went wrong

An error occured during the complilation of the requested file, or one of its dependencies.  Could not write to the output file ‘C:\Windows\Microsfto.NET\Framework64\v4.0.30319\App_web_wopiframe.aspx.9c9699a8.toytrntu.dll’

What we found was that when the WAC farmw was created that the OpenFromUNC parameter was set to true, but the OpenFromURL parameter was set to false.  When we set the OpenFromURL was set to true, the site started to work correctly.