The problem occurred after a BIOS update. The support folks worked with me over several days to no avail. The unit was replaced, under warranty, after 2 weeks from the "no boot issue" date. I like the unit a lot even though I only had it a little over 2 months. I received the replacement unit a couple of days now and I have been working on it with no issues. Remarkably, I was able to retrieve my data from the older unit, with no loss. I will return the older one this week.
I also hope to return to my previous confidence level with my Nuc, soon. Will I buy another one in the future ....... yes I will and will highly recommend it to others.
My thanks to Customer and Tech support who were great.