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AD7091 VSWR Return Loss Measurement Software 2.0 - Error 7

Hello I am getting the following error when trying to change the power and frequency using this software. 

Error 7 occurred at GPIB Write in>AD7091_Main

LabVIEW: File not found. The file might be in a different location or deleted. Use the command prompt or the file explorer to verify that the path is correct.
Nonexistent GPIB interface.