Causes and solutions:
① The 5V switching power supply voltage is unstable or there is no voltage output.
Check whether the green indicator light of the control card is on and whether the 5V voltage is stable, replace the 5V switching power supply.
② The USB cable connecting the control card to the computer is loose.
Replug the USB cable.
③ The control card driver is lost.
Open the computer device manager to see if there is a USB device with a question mark, and reinstall the control card driver.
④ The control card is broken
Replace the control card.