The black screen and the message mean that the new firmware wasn’t written or the copying was interrupted for some reason. The "boot code" is inherent to the processor, so what is needed is to get the firmware copied and restart.
The first thing is to try the update again. Because there is no firmware running, it is necessary to unplug the battery to put the Cobalt in bootloader mode. Then you can try the firmware update again just by plugging the USB adapter without the battery being installed. Here is a link to instructions for removing and replacing the battery:
Dropbox
The Windows program should be able to see the Cobalt when you are connected via USB and you can try again. Afterwards you will need to unplug USB and re-install the battery.
This Windows program has not been maintained or updated, but it still seems to work for most people. If you still have problems and have access to a Mac, the Mac updating program for the Cobalt 1 is a bit easier to use and might be worth a try.
The Cobalt 2 doesn't require any specific program for updating firmware, but the Cobalt 1 does.
If the non-working button is due to a corroded magnet, that is a very easy fix. You can check this out by removing the top cover and trying the switch with another magnet.
Dropbox
If this works, then all you need to do is to obtain a replacement magnet. Let us know if that's the case.
Ron
