Hi Dan, when you connect USB, will the green LED of battery charge light?
Can you also try below steps:
– Disconnect your keyboard from the Mac
– Open the Audio and MIDI utilities app on your Mac, open the MIDI devices window.
– You should see all devices previously connected to your Mac
– Select all devices listed as a CME or Xkey
– Delete all of them
– Press the “Reinit MIDI” button
– Then, open the disk utilities, select the drive on which you OS is installed and launch a “repair disk permissions”.
– Reconnect your Xkey