Sorry to hear about the issue. It’s not clear to me why firmware update would cause the logging to stop working. It’s using the same SD card library, and file format has not changed at all. I would suggest that you take out the microSD card (located close to the top edge of the circuit board), reformat it and try again. Also, if you have a spare microSD card, give that a try. You can format the microSD card to either FAT32 or FAT (if you have a brand-new microSD card, it should work out of box without reformatting).