I am getting a message on the GM of High Sierra on my iMac that " You are not protected. Cannot connect to service. What could be causing this problem? It was working until I had to convert back to NFS & recovered from a backup.
You already have answered your own question as it seems.
Change of filesystem and restoring a backup likely have messed up the installation.
But before repairing or a clean installation, I suggest to change your DNS to the one from Google and see if it makes a difference.