If you can still see the BOOT volume on the microSD card that could not be backed up, do this:
(1) Open the BOOT volume, and you should see a file that is named "zwo_license" in it.
(2) Copy this single file to your desktop. Eject the microSD when it is done.
(3) Next, take that backup copy from the other ASIAIR, and restore a blank microSD card from it. After the new microSD card has finished restoring, mount this new microSD on your computer (it should also appear as a volume called BOOT), and send the "zwo_license" file in the new microSD card to the trash. Empty the trash.
(4) copy the "zwo_license" file on your desktop (from step 2) over to the BOOT volume of the new microSD card.
(5) Eject the new card. This card should be usable to boot up your second ASIAIR.
If the new card boots up, you may want to immediately back it up, so that you have backup copies for both of your ASIAIR.
Before you remove the microSD card from the ASIAIR, be very sure that you first do a soft shut down, then wait until the green LED (SD card activity LED) to finish flashing (then wait another 10 seconds, just for good measure), and only then removing power from the ASIAIR.
Remember never to remove the microSD card from the ASIAIR before doing both a soft shut down, and removing power. I have a feeling that many people are causing microSD card failures by not shutting down and then powering down the Raspberry Pi properly. Never remove the microSD card when the ASIAIR is powered on.
It is best to not re-use the original card that had failed to back up; it may have permanently bad cells.
Clear skies,
Chen
