I ran into this error when I tried to run this blog (BlogEngine.NET | Open Source Blogging Platform) for the first time. I thought I had installed everything on my IIS Server but still the error.

When I searched for the error HTTP Error 500.19 and error code : 0x80070021 I stumbled upon this StackOverflow article. It was then easy to solve by following the steps below.

Valid for Windows Server 2012 with IIS 8.5 but it should work for later versions too.

• Go to Server Manager, click Add roles and features
• In the roles section choose: Web Server
• Under Security sub-section choose everything (I excluded digest, IP restrictions and URL authorization as I don't use them)
• Under Application Development choose .NET Extensibility 4.5, ASP.NET 4.5 and both ISAPI entries
• In the features section choose: NET 3.5, .NET 4.5, ASP.NET 4.5
• In the web server section choose: Web Server (all), Management Tools (IIS Management Console and Management Service), Windows Authentication - if you are using any of it