Hello,
To access a given GPIB resource in LabVIEW, you should use either the GPIB VIs or the VISA VIs, but not both at the same time. That is, you can use either
GPIB: Use the GPIB Write and GPIB Read VIs located in the All Functions -> Instrument I/O -> GPIB palette
or,
VISA: Use the VISA Write and VISA Read VIs located in the All Functions -> Instrument I/O -> VISA palette
Best Regards,
JLS