No, I did not down grade to an older version. Let me try to summarize and be accurate:
My batteries were at 2.0 volts combined.
With low batteries, firmware updates using Nexus 5 running Marshmellow appeared to always work. Updates using a Nexus 9 running Lollipop may have always failed.
With the low batteries, the app always reported connecting to the bootloader and the LED on the meter was always a repeating pattern of 2 longs and 2 blips. I can’t say where in the cycle was the start/end. It could have been 2 blips followed by 2 longs, or some other…
Replacing the batteries without further changes to the firmware (had previously been flashed using latest app) made the meter functional.
Selecting manual voltage range results in 600v range being selected. Once it is selected, the app crashes immediately on connection. Restarting, deleting data and reinstalling all fail to fix it. The problem state is stored in the meter and meter reset was required to recover.
I was not expecting dead batteries. Should a early first run meter with very little used and stored in hibernate mode have dead batteries?