Failed to access IIS metabase

The error can be caused due to the user ASPNET don't have access to IIS metabase, or the ASP.NET is not installed in the IIS properly. To fix this issue, start the command prompt and go to C:\WINDOWS\Microsoft.NET\Framework\<.net version>\

And run

aspnet_regiis -ga ASPNET

Replace ASPNET with any other user that might be runnig the ASP.NET.

Then run:

aspnet_regiis -i

This will install the ASP.NET into the IIS.

Note: You might need to recycle the Application Pool. Source: ASP.NET IIS Registration Tool (Aspnet_regiis.exe)