Resolved! I am having trouble getting the RTC to work with battery backup. I am using LSE as the clock and I have enabled the backup domain. I can set the date/time values as expected.
But when I remove power (with the 3V battery still connected to Vbat) the date/time values freeze. That is, they remain where they were when to power was removed. How do I make the RTC continue to run during power down? Any help is appreciated.