As
@VIOFO-Support stated, make sure the microSD card has been formatted with a FAT32 file system before copying the two firmware "bin" files to the root directory of the microSD card file system. I use a separate 32GB microSD card for this purpose which allows me to retain all of the files on the "regular use" microSD card for that dash camera.
The front camera firmware filename should be "FWA229S.bin" (minus the quotes). The rear camera filename should be "EthcamTxFW.bin" (minus the quotes). Install the microSD card into the dash camera and power it up. The leftmost LED should start quickly blinking indicating it's located the front camera firmware file and the front camera firmware is being updated.
When the updating of the front camera firmware completes, it will reboot the dash camera and it [may] prompt your to select the camera's language, time zone and then it may prompt to format the microSD card. You need to answer no to the formatting since that will wipe away the rear camera firmware file that has yet to be installed. Once the dash camera has fully booted up, it will detect the presence of the "EthcamTxFW.bin" on the microSD card and it will initiate the rear camera firmware update process.