Can't get IIS Express and .Less Files to work

Question

I have inherited a .NET core project that uses .Less files but I cannot get it to run locally in IIS Express.

I followed this page to add .Less Mimemap to the global config https://johandorper.com/log/add-less-to-iis-express But now I am getting a 500 error, before I was getting a 404

The 500 error I am getting is:

I have also tried adding .less to the projects webconfig with no difference.

All the .less files are in the content folder of my project, do I need to do anything else to make them load (I have never used .less before)

Answer 1

Found the issue, it's permissions. I needed to run Visual Studio as an Administrator