The trouble is the instructions on the Resol website for this update are wrong. I found helpful instructions on the way back machine, but even those had to be adjusted.

Here's what worked for me:

1. Make sure you are on firmware version 1.4.5 or lower. Go to http://192.168.1.100/cgi-bin/get_resol_device_information (replace 192.168.1.100 with your DL2’s IP address)
2. Format your SD card. Formatting on the Mac with MS-DOS(FAT) didn’t work for me. I ended up formatting it on my Panasonic camera.
3. Insert the freshly-formatted card into the DL2, wait till the flashing green light turns solid. . .
4. Take the card out and put it in your computer: you will see a folder DL2 with the log files in it. If you don’t, the DL2 hasn’t recognized the SD card.
5. Unzip the firmware.zip file you downloaded from Resol. At the top level, you will see firmware.bin and firmware.yml. Copy them to the top level of the SD card and rename them resol-dl2-firmware.bin and resol-dl2-firmware.yml.
6. Eject the card and insert it into the DL2. The green light will blink green and turn solid. After a few minutes, go to http://192.168.1.100/cgi-bin/get_resol_device_information again you should see version 1.4.7.

Hopefully Resol's instructions for updating from 1.4.7 o 2.x are correct. I haven't tried it.