It mostly happens when IIS is installed after .NET is installed. So in this case we need to make use of aspnet_regiis.exe utility.
1) Go to command prompt
2) Go to the following path
depending on the version.
3) Enter “aspnet_regiis.exe -i”
4) It will display the message finished installing
5) Open your IIS
6) Select web service extensions
7) Click on Allow for ASP.NET v2.0.50727
That’s it . Now the IIS has been configured properly