Microsoft PowerPoint Web App - "The service is temporarily unavailable"

Question

Hi all, 
I have had a problem with Office Web Apps/SharePoint 2010 now for over a week. When trying to access PowerPoint Presentations I receive the error:
I have looked through all of the Technet articles on this error and more, but still I have had no luck. The Excel and the Word viewer both work fine but this doesn't.
I have checked that the Word, Excel and PowerPoint services are running on the Web Front End Server and also on the Application Server. They are all using the "SharePoint Web Services Default" application pool which has dbcreator access to the
content database.
I am receiving an error in the event logs:
This error reads: "A word or PowerPoint front end failed to communicate with backend machine...." the url then seems to vary between the front end server and the application server.
This exact same error is also appearing when checking in the ULS Logs. I have been working to repair this for days but I am out of ideas, all of the latest patches and CU's are installed on the servers.
I would massively appreciate any help given with this.

Answer 1

Hi Adam,
Here is the link for Event ID 8011 for reference:
 http://technet.microsoft.com/en-us/library/jj663079(v=office.15).aspx
Please refer to the kb below for possible solutions:
http://support.microsoft.com/kb/2028346/en-us
In addition, you could try reset account password which is used to set up service application via:
Go to CA > security > configured managed accounts > modify > change the password now > use the current password > type password > OK.
Regards,
Rebecca Tu
TechNet Community Support