Communication with HP4194A via GPIB

Hello everyone,
I believe that there are many capable engineers, and i will appreciated it very much if someone can help me solve the problems i encountered.
I'm using an old instrument called HP 4194A impedance/gain-phase analyzer.In the beginning, we operate it manually, however, my boss ask me to control this instrument by program now. I am a beginner, i don't konw how to solve these problems at all.
i used a Agilent 82357B GPIB/USB converter to connect HP 4194A and PC. When I plugged the GPIB interface into the instrument, Agilent Connection Expert automatically recognized the instrument and sent the command, but received the following error message: The instrument failed to return an IDN string. Does it mean failing to connect the instrument.
Is there anyone that encountered the same problem? can you tell me how to solve this problem? All help would be gratefully recived.
/Regards John 洪