Have you checked the firewall settings to make sure the port 80 is open to public? That could be the problem. If it is and you still can't access it then turn the firewall off and test it again. If you can access it then the firewall configuration needs to be changed.
You need to make sure you installed the web server rolls. You can do that using server manager.
You would be better off with Windows Server 2019 or at the very least 2012. @008 is dated and support for it is expired.
We are pleased to announce the latest version of Core Configurator built and designed for Windows Server 2008 R2 x64 Core edition!
It is completely open source so it can be amended and change to fit your requirements, this version has been a year in the making and has been written in powershell...