Looking at how to get WordPress running on Windows Server and allowing auto update to work. This is what I did and it seems to work.
I used the Web Platform Installer to install WordPress, I then downgraded it to WordPress 4.7, I just copied the files over the install. So I could test the upgrade process. When installing using the Web Platform you need to provide random generated key’s, I found this https://api.wordpress.org/secret-key/1.1/salt which generates random keys for you, but the Windows Installer doesn’t like $, which is a tad annoying.
Hope this helps. Have fun :-)