It would be great if you could have the exact / detailed error by changing customErrors to Off in your web.config. Sometimes you get the errors in Event Viewer / Windows logs / Application from windows.
You probably don't have asp.net installed / configured on the IIS. Here is a guide to install it :
https://learn.microsoft.com/en-us/iis/application-frameworks/scenario-build-an-aspnet-website-on-iis/configuring-step-1-install-iis-and-asp-net-modules