Issue

Users cannot open excel files in SharePoint 2010 from the Library and get an error
"This workbook cannot be opened because it is not stored in an Excel Services Application trusted location. To create an Excel Services Application trusted location, contact your system administrator"




Initially what users do - They contact SP admins and ask them to add library to trusted file location (as error says) but in SP 2010 it's not the case 

Cause

By default the files are designed to open in browser . So it is checking for trusted location   

Resolution

  • Go to the Library
  • On the top click on Library and go to Library settings 
  • Under General Settings you will find Advanced settings
  • Over there you will find the option which by default is set to open in Browser
  • You need to set it to Open in Client and there you go 
  • Click OK and you are done