You can try resetting the MCU/firmware, it might allow you to reinstall a firmware. It works most of the time, if you really bricked the MCU, then there is not much to do.
Open the keyboard
Reset the MCU
Upload a Firmware
Close the keyboard
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How to open the Truly Ergonomic Keyboard:
http://geekhack.org/index.php?topic=38943.msg803906#msg803906Info provided by Truly Ergonomic:
Please be aware that if you open the keyboard, you will dismiss all guarantees.
1. First remove the 9 screws that hold the palmrest, and then remove the palmrest.
2. Then remove the top 2 screws and the 4 additional screws that were hidden by the palmrest.
3. There are 2 additional screws under the back label – located on each of the top corners. Press the label on each corner with your thumbs or fingers to feel where the screw cavity is located, and then use a screwdriver or cutter to split through the label.
http://www.trulyergonomic.com/store/image/data/Truly_Ergonomic-underside_all_screws.jpg4. After all screws are out, you need to 'horizontally-twist' the top-body against the bottom-body as there are 6 'hooks' that hold these two parts together; 4 hooks on the backside where the cable is located, and 1 hook on each side.
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How to Reset the MCU
http://geekhack.org/index.php?topic=38943.msg787293#msg787293With the keyboard plugged into your computer:
Touch Pin 1 and pin 36 - the upper pins of each side of the chip when the round angle mark is at the top left.
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Upload default firmware:
https://www.trulyergonomic.com/store/firmware-upgrade--truly-ergonomic-mechanical-keyboard------------------------------------------------------------------
Hope it helps.