When you see the lock screen on the Huum Uku controller shown below, this means it was put in child lock mode. 

In order to turn the child lock off and activate the screen, follow the directions below:

• Press and hold the button
• Turn the dial 90 degrees to the right and then back
• Then turn the dial 90 degrees to the left and then back

You should see the controller screen reappear and be able to operate it as normal. 

If you are still experiencing any issues please submit a support ticket.