Problems related to HART 475 field communicator

I was going to calibrate the control valve with the DVC 6000 series smart positioner, but the HART 475 field communicator displays no device found when it is connected to the positioner and why is that

Check for the voltage on the hart, you should get around 18-24v, which means that your cable is good and there’s voltage present. Use your 789 as independent loop power and turn on the 250-ohm function. Then connect the 475 and use the valve link.