It’s not uncommon to run into an error or two when you first setup Office Web Apps. Here is a common one you might run into with the PowerPoint Web App and it actually has a simple solution. You might encounter the error below when using the View in Browser or Edit in Browser functionality in SharePoint with a PowerPoint file.
The service is temporarily unavailable. Please try again later.
I thought this was kind of a strange error, but I’ve seen worse. I proceeded to begin my usual troubleshooting process. I opened up the ULS logs and I actually found nothing. This is actually one of those few cases where there is no information in the ULS logs but there is information in the Application Event Log. I saw an error listed and it provided the exact answer to me.
There are no instances of the Microsoft.Office.Server.PowerPoint.SharePoint.Administration.PowerPointWebService started on any server in this farm. Ensure that at least one instance is started on an application server in the farm using the Services on Server page in Central Administration.
Sure enough, I opened Services on Server in Central Administration and the PowerPoint Service had not been started on this particular virtual machine. I started the service and the error was resolved.