After I posted this message, I did some additional research and found that this is NOT an isolated incident nor is it affecting 1 or 2 people.
This has happened before, and Google took a few days to fix the issue in each case.
This situation appears to be similar. Google's forum has a very recent thread on this subject: https://support.google.com/calendar/thread/110723186/why-are-my-embedded-public-calendars-not-displaying-without-a-sign-in?hl=en
Frank