The spindle motor is not running while other functions of the CNC machine are fine.

Input spindle forward M3 S1000 or spindle backward M4 S1000, no response, but other functions like tool changer, coolant and axes moving are normal.

Check below:

1-      Are there signals output for spindle forward or backward from CNC controller?

2-      0V~10V analog signal from the CNC controller is ok or not?

3-      Any open or short circuit of the CNC control cables?

4-      Is the frequency inverter broken?

5-      Parameters of the frequency inverter are set correctly or not?

6-      The spindle relays for forward or backward and the spindle motor are in open circuit or not?

In this case we checked the CNC controller has no 0V~10V analog signal output, the reason is connection mistake, correct it and the problem solved.