It sounds like this is an issue with the installation of NI-VISA being faulty. Have you tried uninstalling and reinstalling, or force reinstalling NI-VISA? Is this the first time you installed NI-VISA on this computer?
Also, this thread is 4 years old so you may want to post your question in a new thread so that it gets for visibility in the community.
"Failed to install command set '34401 Digital Multimeters'. Could not load file or assembly 'Ivi.Visa.Interop, Version=18.104.22.168, Culture=neutral, PublicKeyToken=a128c98f1d7717c1' or one of its dependencies. The system cannot find the file specified."
I get the above error when I try to use Agilent 34401A digital multimeter with the National Instrument GPIB-USB-HS adaptor combination. This is happening when I try to install the command sets for Agilent 34401A using Keysight command expert.
This is what exactly I do in keysight command expert
New Instrument >> Connect to a real Instrument >> Next >> Selected ESG -D4000B - B.03.86 - US38440605 >> Next >> Selected ESG Signal Generators >> Next >>Add to my instrument >> Getting an error after progress window..