Dear @amario
The problem has been solved by creating the link following this post https://fluka-forum.web.cern.ch/t/executable-returned-rc-134/3452
I also download the Neutron library by using https://fluka.cern/download/neutron-data-libraries
I’m not entirely sure whether the issue was resolved by creating a gfortran link or installing the neutron library, but the good news is, Fluka can now run by using both the command line and Flair.
Thank you for your time