I was pleased to see with the latest Windows 10 and Windows Server 2016 the old 260 character restriction for folder and file names can be overcome.
I've just installed Windows 2016 on a new machine and have followed the steps to enable long paths (as detailed here), and am still getting messages telling me files cannot be copied or folders created because they would create a long path name.
What have I done wrong is there something more I need to do?
The description of the setting, as seen in the very article that you linked to, says:
This means that even after you turn this on, not every application is going to magically start being able to access long paths. Each specific application still has to be coded so as to "opt-in" to this support.
As of the time of this writing, Explorer.exe and cmd.exe are not taking advantage of this yet. (But they will, eventually... just give it time.)
But I have seen Powershell taking advantage of the new feature: