SharePoint 2010 can't open xlsx file in the browser

Received message "Unable to process the request. Wait a few minutes and try performing this operation again".

Fix:
1. Ensure that Excel Service Application is created and running under "Manage service applications"
2. Ensure that Under "Manage services on server", the Excel Calculation Services is started and running on the web front end(s) of the farm
3. Ensure that the Excel Service Application is associated with the proper web applications under "Configure service application associations"

Update: Excel file can't be edited in browser without Office Web Apps.