Error: Cannot write configuration file due to insufficient permissions
This error usually comes when you are using source control over your project and you have explicitly not check out your file for modifications . Try check out in source control software you are using and then copy the file to inetpub and try again the process of modifying .Net trust level from IIS manager , it should work now .
3ec41a32-de9b-4e57-9cdf-bfc37f99b500|0|.0|96d5b379-7e1d-4dac-a6ba-1e50db561b04
IIS
insufficient permissions