One other thing I have tried and I am not sure if it will help with troubleshooting this is, if I manually download the update that Windows Update says is required, I get a message saying "The update is not applicable to your computer".
I get the same message if I download any SSU including the latest one. The SSU isn't showing up as an available update but I don't see it installed on the server either.
I hope that provides more information.
Neal