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Hopefully it will be useful to someone who is struggling to resolve this issue.

Following is Checklist points to resolve this issue

1. Verify the Word View Services and PowerPoint Services are started on OWA Server.

2. Verify that Word View Service Application and PowerPoint Services and their proxies are created

Go to Central Admin -> Application Management -> Manage Service Application 

3. Verify the Service Application proxies are configured to the dfault proxies of the Web Applicaion 

Manage Web Application -> Select Web Application -> Click on Service Connections on the ribon -> Verify OWA Service Apps are checked.

4. Verify the App Pool account that is configured for the Word Viewing Service and PowerPoint service is added as login account with DB Owner Permissions to the Content database of the Web Application

5. Run the PSConfig on all the servers. Use either SharePoint Configuration wizard or powershell psconfig command to perform this operation

6. Re-create the PowerPoint Service app and Word Viewing Service App if they are already created.

7. Restart IIS on all servers

8. Finally Restart all servers in farm