Critical software update is required for your Mac Infinite Loop

My A1398 MacBook Pro stopped booting today. It is in an infinite loop stating that, "A critical software update is required for your Mac. To install this update you need to connect to a network". After connecting to the network an error appears saying the update did not install properly. It presents 2 options: (1) Shutdown (2) Try Again

Computer boots in safe mode. In safe mode I upgrade Sierra from 10.13.3 to 10.13.6. App store is not recommending any additional updates. Of course upon reboot the same message appears. I have tried NVRAM reset, etc and nothing works.

So Apple has turned my computer into a brick for an update that apparently cannot be installed in Safe Mode. Gee Thanks.