Firstly, test that any faults with your LED’s and LCD’s are not triggered by poor power supply by ensuring that your QCon is connected correctly. If using a powered USB hub, try plugging the connecting USB directly into your computer. It may also be useful to completely reboot your system - a multitude of seemingly intangible problems can be solved in this way. Lastly, test that the power supply unit itself is working.
If problems persist with your LED and/or LCD display, proceed with the following;
Firstly, turn off your QCon, then press and hold the REC button on [Ch 4] while turning the device on.
This will load the device into LED Test Mode, which should light up every LED and LCD on the device for testing. This should help isolate the cause of the issue.