I tried disabling the firewall and opening Kodi, and the NextPVR was still not starting. I rebooted the Mac and checked Kodi and got the same thing - message that PVR manager was starting but nothing but a spinning circle and a 0% indicator. So I did the re-install Kodi thing over the existing, and this time the NextPVR still wouldn't start. I'm going to "uninstall" Kodi (drag it from applications to the trash), reboot, reinstall Kodi and see what I get. The logging is still on through all of this, I think.
I did the things I said I would do, and after re-installing NextPVR client is working again. Yes, they are on the same subnet; in fact they are plugged into the same network switch.