Word WebApp encountered an unexpected error /Excel WebApp unable to process the request

In one of my newly created web application, the users tried to open Excel/Word documents using browsers. They were getting the following error and I had to investigate.

 I checked all the services on the WFE and Word viewer service, Excel calculation service were running. When i checked the event viewer for errors, I found the following in event viewer, which ringed the bell

Then I checked the Central Admin->Application Management-> Select the web application -> Service connections -> Configure service application associations and found that Excel Service and Word viewing service is not configured for this web application. When I enabled those for this application, users were able to view Excel/Word using browser. Hope this helps for you!!!