The permissions granted to user 'domain\username' are insufficient for performing this operation. (rsAccessDenied) SQL Server Report Server (SSRS)

Reporting Services uses role-based security to grant user access to a report server. On a new report server installation, only users who are members of the local Administrators group have permissions to report server content and operations. To make the report server available to other users, you must create role assignments that map  user or group accounts to a predefined role that specifies a collection of tasks.

Verify that sufficient permissions have been granted and windows user account control (uac) restrictions have been addressed

It is an insufficient  privilege for current user you are running the report, give that user a privilege to run report / report folders

Start Internet Explorer As "Run as Administrator"
Open Your Report Server URL (http://'ServerName'/'ReportFolder')
Go to Site Settings

Security->New Role Assignment

Add DOMAIN/USERNAME or DOMAIN/USERGROUP

Step 2

Go to Folder Settings

Security->New Role Assignment

Add DOMAIN/USERNAME or DOMAIN/USERGROUP
Check the Report URL