The NeqSim Excel user interface is installed by unziping the neqsimexcel2.4.1.zip file, and open the NeqSimExcel.xlsx file.
To use NeqSim fluid models in a Cape Open compatible process simulator, you will need to install the NeqSim-2.4.1.msi file. This will install the Cape Open interface for NeqSim and register it on your computer.
See documentation:
https://github.com/equinor/neqsimExcelCapeOpen/wiki
In this case NeqSim do not register correctly during installation. You will have to run the NeqSimRegistration.exe file in the NeqSim installation directory (C:\Program Files (x86)\Equinor\NeqSim/..).