If the blue light doesn't show from the beginning, after troubleshooting cable issues, please directly measure the voltage at pins 2 and 3 of the mainboard port to see if there's 5V voltage. If not, please contact cs@creality.com to replace the mainboard.
If the power supply is normal, please measure the voltage between pins 1 and 2. When the filament break detection light is working normally and the cable is fine, the voltage should be around 2.5V without filament, and about 0.28V when filament is inserted. If the voltage is abnormal, please contact cs@creality.com to replace the mainboard. .