MVC Core error - HTTP Error 502.5 - Process Failure

If you are deploying your project to Internet Information Services and you get the error below, there are several possible reasons according with microsoft.

Possible reasons:

• If you published a self-contained application, confirm that you didn’t set a platform in buildOptions of project.json that conflicts with the publishing RID. For example, do not specify a platform of x86 and publish with an RID of win81-x64 (dotnet publish -c Release -r win81-x64). The project will publish without warning or error but fail with the above logged exceptions on the server.
• Check the processPath attribute on the element in web.config to confirm that it is dotnet for a portable application or .\my_application.exe for a self-contained application. For a portable application, dotnet.exe might not be accessible via the PATH settings. Confirm that C:\Program Files\dotnet\ exists in the System PATH settings.
• For a portable application, dotnet.exe might not be accessible for the user identity of the Application Pool. Confirm that the AppPool user identity has access to the C:\Program Files\dotnet directory. Confirm that you have correctly referenced the IIS Integration middleware by calling the .UseIISIntegration() method of the application’s WebHostBuilder().
• If you are using the .UseUrls() extension method when self-hosting with Kestrel, confirm that it is positioned before the .UseIISIntegration() extension method on WebHostBuilder(). .UseIISIntegration() must set the Url for the reverse-proxy when running Kestrel behind IIS and not have its value overridden by .UseUrls().

I got this error, but in my case the problem was I didn't declared the environment variable ASPNETCORE_ENVIRONMENT, so the application wasn't able to get the appsettings..json file; after I added the variable I restarted the server and my site worked just fine.