I have the same problem. I plugged my keyboard in a usb port hub which was plugged to the wrong transformer and resulted in a 12v voltage instead of 5v. My keyboard has since stopped working, but I’ve been trying to figure out what is wrong. I opened it up and saw with a multimeter that current was flowing since there is a voltage difference between the positive and negative cable. Even with that, the keyboard doesnt seem to be recognized by my computer. No sound or any light when plugging it and nothing is working. I am not sure where to go from there, it seems that the current passes but not the data allowing the keyboard to send commands.