download problem

dear all
i download programme on ML and HMI separately but when connected both together they dont communicate shows error 386 or 286 something.after sometime of trial it communicate properly i dont know why....can we put password on HMI panelview 300 micro

Post the model numbers of what PV you are using. You need to set the comms correctly, or your app will not work, and give you an error code.
Post the correct error code, and we will try to help. Usually a cable problem or a DH-485 problem.