Issue:
In the list of Web Service Extensions in the IIS Manager one of the versions of ASP.Net that is installed on the server is not listed. You can verify that the desired version of ASP.Net is installed by looking in the default installation folder.
%systemroot%\Micrsoft.NET\Framework\<version>
Cause:
The ASP.NET version has not been registered with IIS, or was removed.
Solution:
You can re-register the desired ASP.NET version with IIS using the aspnet_regiis.exe utility
1) Open a command prompt
a. Type the following
"%systemroot%\Microsoft.NET\Framework\<version>\aspnet_regiis.exe" –i
Where <version> is the actual version of ASP.NET that needs to be re-registered with IIS.