Thanks for your quick responses! The shipping constraints are good to know; going forward I won’t remove the battery after setting the clock.
I was able to confirm, using PCSync, that my development mayfly does lose its clock setting with power and coin cell disconnected. No surprise there. And then I disconnected USB power again, then reconnected and uploaded my MMW testing sketch, still with no coin cell installed. The Mayfly connected to NIST via 4G successfully, set its clock, and uploaded data properly to MMW. So, it seems that the clock/battery question is not the cause of Jake’s board not uploading data. Not sure what is though. The UUIDs are all set properly as far as I can see. The Mayfly’s modem (and SIM) were transferred from an operational Mayfly into this newly-programmed board.