If you recently replaced either the main control board or an option card, their firmware versions might not match. The drive cannot interpret the data structure of an incompatible card. 4. Failed Option Card or Control Board Hardware
If the drive is programmed for a 4-20mA loop and your meter reads 0mA, look for a broken wire, loose terminal screw, or a failed master controller (PLC/potentiometer). Step 4: Mitigate Electrical Noise yaskawa error code h66