Hello,
Driver requirements for Agilent GPIB drivers changed from MATLAB R2015a to R2017a http://www.mathworks.com/help/releases/R2017a/instrument/driver-requirements.html http://www.mathworks.com/help/releases/R2015a/instrument/driver-requirements.html
Please install the support package "Instrument Control Toolbox Support Package for Keysight IO Libraries and VISA Interface" in MATLAB R2017a which will install the appropriate drivers.