.NET 4 BEFORE IIS

When installing anything in Operations Manager 2012, .NET 4 must be installed before IIS. Otherwise, certain steps will have to be taken to resolve the issue.

From the Microsoft DOC:

Important

You must install IIS before installing .NET Framework 4. If you installed IIS after installing .NET Framework 4, you must register ASP.NET 4.0 with IIS. Open a Command prompt window by using the Run As Administrator option and then run the following command:

%WINDIR%\Microsoft.NET\Framework64\v4.0.30319\aspnet_regiis.exe -r