I get your frustration, and the RTC battery was removed AFTER testing everything else I literally wrote my last message and edited to add the RTC after attempting it.
Logic:
Troubleshooting — IoTaWatt 02_03_20 documentation mentions failure of RTC to init, reseating the battery should force reinitilisation.
backed up by Always dull red light - #20 by Akos - mentions resolved with RTC reset.