Note: This 401 error is related to reports that do not use Reporting Services to run, such as the Executive Summary report. For HTTP 401 error permission errors (only occurring on reports that use Reporting Services to run), please refer to this KB Article:
Executive Summary reports fail with the following error "The remote server returned an error: (401)". If you open the diagnostic file, it will look this this:
1- Go to system tab > Configure page
2- Scroll towards the bottom of the page and click on the gray button "Change Reporting Config"
3- Once the window opens, under the field "Report URL Base", please change the value to: http://localhost/