I am currently working on Report Builder 2.0 with Reporting Services 2008 and am trying to connect to a SharePoint 2013 site using an XML data source query. SharePoint and Report Builder/Services are on different servers. I enter the correct connection string to the SharePoint lists and have tried to connect through "use current Windows user," manually entering credentials as Windows credentials, and "do not use credentials" but each of these options lead to a 401 unauthorized error. I looked around for solutions and have gotten suggestions of double hop or untrusted connections. Does anyone know what the problem is and how I would go about resolving it?
Try going into the SSRS Config utility and set up an execution account, then grant that execution account read access to the site you're trying to get to.