So far I’ve tried reformatting the card, rebooting the meter via the reset switch and pulling the batteries, rebooting my phone, turning on and off the logging via the phone, changing the logging settings, no go.
What it’s doing now is a weak orange light for a little over a second, repeated every 10 s or so, whether or not I have logging enabled in the app. The only thing that changes the weak orange light is to remove the SD card; then I get only a very short orange flash every 10 s or so. No data is written to the SD card. Meter works fine otherwise, just no logging.