Here is what today brought.
Firstly, I discovered that after restoring the ATV, my problem logging into Nextflix was because I was using the wrong email address. After fixing that, I could login but still got the "cannot connect to Netflix service" message with no numeric code.
Next, I called Netflix and, after explaining that I had already tried changing the DNS to 8.8.8.8 and power cycling the ATV, which sometimes worked and sometimes did not, they suggested that I power cycle my Airport Wireless router.
That solved the problem for now. The Netflix rep indicated that if the problem persists, then the router may need to be reconfigured.
Oh my. One more day in which to return the ATV to Amazon. What to do? What to do? Life on the bleeding edge of technology!
Needless to say, my iMac, also on the wireless network, has no problem playing Netflix videos.