The VFD must be connected directly to the motor, with no disconnects or relays between the the VFD and the motor. The existing spindle motor pushbutton station must be wired into the VFD control terminals, or must have intervening relays if it also needs to be connected to the control cabinet. The VFD has a set of what they are calling ''multi-function inputs'', these are what controls the VFD. These inputs are internally powered by the VFD and can not be connected to 120V external power. You are going the have to do some rewiring to make everything work correctly. I suspect there are 5 or 6 wires from the pushbutton station that went to the power cabinet that ran the motor starter and E-stop. You don't need the remote operator station that is available for the VFD. It is possible you might need a couple of small ''ice cube'' relays to interface the controls, but I don't think so. I don't think the CNC controller controls the spindle motor at all, or even knows if the spindle is running or not. The next step is to identify the wires from the pushbutton station and match them with the terminals in the power cabinet. Once you have that information, I can help you with a diagram of the original, and then the modifications needed for the VFD install. . .