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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 PowerPoint Services is started on OWA Server.

2. Verify that PowerPoint Service App and their proxies are created

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

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

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

4. Verify the App Pool account that is configured for the 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 if they are already created.

7. Restart IIS on all servers

8. Finally Restart all servers in farm