Hello,
If I understand the post correctly, you have two identical analyzers, one of which works with the program, and the other does not. If this is the case, one thing that can be different about the instruments is the address. Suppose one instrument has address 4 and the other has address 5. Then, if your program attempts to communicate using a VISA Resource Name, say, GPIB0::4::INSTR when you are attempting to communicate with the instrument which has address 5, you should get an error (probably ENOL; see description below). If you receive an error, feel free to repost with a screenshot of it and perhaps it will elucidate the issue more clearly for us.
ENOL Description:
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ENOL usually occurs when a write operation is attempted with no Lis
teners addressed. For a device write, ENOL indicates that the GPIB address configured for that device in the software does not match the GPIB address of any device connected to the bus, that the GPIB cable is not connected to the device, or that the device is not powered on.
Thank you,
Best Regards,
JLS