Yup, you wiped out the brain of the device a keyboard in this case. Any device that is computer based like a computer, smartphone, keyboard, and on and on has PROM or shorthand ROM chips it stores its basic code to get the device to bootup enough so it can then load the operating system. You appear to have interrupted the ROM being updated so in basic terms you wiped out the brain of the keyboard.
So the brain needs its code reloaded or replace the ROM with one that still has the correct startup code. Any authorized dealer can do this and if you feel handy with tools maybe they can talk you thru removing the mainboard and shipping it to them to be updated.