Reporting Services Configuration Tool unable to connect Instance error - In windows 2012 server having SQLServer 2008/R2 named instance

When opening the Reporting Services Configuration Manager attempting
to connect to a named instance, no instances are available in the Report Server Instance drop down list, and when the find button is pressed the error

 "No report servers were found.

 Details:

 Invalid Namespace"

Resolution

Go to the path -Microsoft SQL Server\MSRS10.SQL2008\Reporting Services\ReportServer\bin\reportingservices.mof .

Take a backup of the file before modifying 

Replace the the instance name in all places with your correct instance 

name in the .mof file . your named instance is SQL2008

//Name = "RS_SQL2008" change to Name = "SQL2008"//

Next Step : Open cmd as Administrator and Run the below command 

mofcomp.exe "C:\Program Files\Microsoft SQL
Server\MSRS10.SQL2008\Reporting Services\ReportServer\bin\reportingservices.mof"

After doing this , Please Restart WMI Services from Services.msc

and open Report Service configuration Manager console.

This time you will be able to see the Server and Instance details .

Good Luck