Started using Sharepoint 2013 after several years which I didn’t touch this product. M$ did an amazing job, and I consider this one of the easier application to integrate with.
One thing that I liked is the office 365 (web version of Office).
When I try to refresh data using the web version I got a nasty error “the data connection uses Windows Authentication and user credentials could not be delegated. The following connections failed to refresh: PowerPivot Data” although my connection was clearly using SQL authentication in the query string
While searching for answer I found this article but sadly it is not related, since as said I am using SQL authentication.
I decided to review the connection and found a new option for “Excel services: Authentication Settings”
And when opening I saw that the default was use the authenticated user account (which I don’t need)
The solution in my case, was to switch to “None” and all is good