Unknown code error in Python using NI GPIB-USB-HS

Hi, 

I am using NI GPIB-USB-HS device to control Keithley 2700, Chroma load and Agilent DC power supply. I have all the devices connected and I can see it as the GPIB devices in Python.

But when I tried this self identification command, I get an error saying,

This happens to any command that I try to run. I have the drivers installed. I am not sure where I am going wrong.

Is there any setup that should be done before running these commands? Any suggestions would help. 

Thank you!