Greetings, Dave.
Under Calendar Settings > Integrate Calendar, my calendar ID displays just my email address. It does not look like c3RldmVAbTNp21haWwuY29t.
I have tried other strings that look do like this, such as from the "Secret address in iCal format" URL and from the calendar URL in the browser bar (the bracketed portion: https://calendar.google.com/calendar/u/0/r/settings/calendar/[c3RldmVA...vbi5jb20]?tab=mc&pli=1), but all of these return an error message saying it cannot find this calendar ID.
Why am I not seeing what you think I should be seeing?
Thanks.