Okay, I figured it out. This has to do with a problematic SD card in the controller. I removed the card, found the formatting was corrupt, re-formatted as FAT32 and put it back in. Things worked properly. Was able to get the firmware updated.
Note: the updater program, running in Windows 10, wouldn’t detect the OpenSprinkler controller… UNTIL I started the program using the “run as administrator” option.