When you open a workbook in the browser using Excel Services and get an error, or when a scheduled data refresh fails in PowerPivot for SharePoint, you may see the following error in the ULS logs:
Retrieving the COM class factory for component with CLSID {BDEADF26-C265-11D0-BCED-00A0C90AB50F} failed due to the following error: 800703fa
If you see this specific error, you can fix the error using the following steps:
1. Open Internet Information Services (IIS) Manager.
2. Expand SharePoint Web Services in the left menu.
3. Click on the first ID under SharePoint Web Services and then click on Content View at bottom of the center menu.
4. Select each ID until you see ExcelService.asmx (for Excel Services error) or SSASMidTierService.svc (for PowerPivot error) in the center menu.
5. Click on Advanced Settings on the right menu, note the value in Application Pool, and click Cancel.
6. Select Application Pool in the left menu and select the application pool you noted in the previous step.
7. Click on Advanced Settings on the right menu.
8. Look for the setting Load User Profile, set the value to True, and click OK.
9. Open a Command Prompt and run iisreset to restart IIS.