Error while trying to access Reporting Services Manager for a new installation of Reporting Services.
As documented by TechNet, primary cause is that, on a new installation, only local administrators have access to a report server. To grant access to other users, a local administrator can use Report Manager to create new role assignments.
This fix worked for me:
Content Manager: May manage content in the Report Server. This includes folders, reports and resources.
My Reports: May publish reports and linked reports; manage folders, reports and resources in a users My Reports folder.
Publisher: May publish reports and linked reports to the Report Server.
Report Builder: May view report definitions.
In addition make sure intranet settings are enabled in IE. Even when typing your password in the authentication popup it may not work without intranet settings enabled. See how to enable intranet settings here >>