A user logged into SharePoint 2010 (or later) uploads a PowerPivot workbook and chooses to schedule a data refresh for the workbook according to How to: Schedule PowerPivot workbook data refresh
Reference Step 7, choice C: The user enters a known existing Secure Store Target application ID in the Credentials section inside the "Connect using the credentials saved in Secure Store Service" field.
When the user clicks OK to save the schedule, the following error displays:
"The provided Secure Store target application is either incorrectly configured or does not exist"
PowerPivot uses SharePoint's Secure Store methods to verify the user Administrative rights in Secure Store. The method used to check user permissions requires the user have at least one of these Secure Store Administrator rights before the Secure Store Target Application ID is acknowledged: Create, Manage, or Delete Secure Store Application.
Grant the user permissions using the Secure Store Administrators feature in Central Administration.
In Central Administration browse to Application Management
Click Manage Service Applications
Click to the right of the Secure Store Application link so the row appears highlighted.
Click on the Administrators button and add the user attempting to edit the PowerPivot data refresh schedule (or an appropriate security group including user) to the field.
Click Add, then check "Manage target applications".
Finally, add the user to the Administrators group of the Secure Store target application you wish to use for the PowerPivot scheduled refresh. Refer to Step 11. in the "Create a target application" section: http://technet.microsoft.com/en-us/library/ee806866(v=office.14).aspx#section3