"Cannot connect to a Norton server" after Win10 Anniversary Update

I have 3 Win10 systems on a local LAN.

After applying the Win10 Anniversary Upgrade to one of them, Norton 360 Premier is set up correctly and working as it was before the upgrade with no intervention on my part.

On the other two systems after the Upgrade, N360P says "trial expired, activate".

When I try to activate, it tries to connect for a few seconds and then says "Cannot connect to a Norton server". I have retried this several times over the past 24 hours with the same result. I have tried rebooting Windows, also with the same result.

How can I fix this, please? Thank you!! ..Bill.42..