LEKN standalone controller problem

[regpye]

Part of your problem may be a lack of current capacity of the 5V supply from your computer. The square black connector at the bottom of the picture of an Arduino UNO below is an external supply input. The Arduino specification is for 7-12V at this input. Have a look at the Arduino website for detailed information on power requirements.



https://store.arduino.cc/usa/arduino-uno-rev3

Kit

Thanks for your input.
Maybe I have something wrong with my boards then? I have connected 12 volts to that socket and still there seems to be no power getting to the UNO from there.
The only way I have been able to get power is by using the USB connection. Power to the steppers is by the connection on the CNC shield power connections which doesn't give power to the UNO.
The way I understood it was that if 12 volt was applied to the square black connector, it would be reduced down to 5 volts for the UNO supply, but in my case(s) it is not working