Impossible to access to Cognos Administration

I recently installed cognos BI 10.1 on a Windows Server 2008 R2 environment with IIS 7.5 and SQL Server 2008 R2 for CS
Everything is ok, I can access the portal, QS, RS etc but can’t display the Cognos Administration and I have no error message.

Anyone can help pelase ? :’(

Try to follow this easy steps and make sure you did part for Administration configuration: