Retrospect supports the Microsoft Windows Server Core 2008 R2, 2012, 2016, 2019, 2022. These versions of Windows require special steps for Retrospect installation by the command line.
To install Retrospect on Windows core, use the following command (for Retrospect 19):
msiexec /i 'Retrospect 19.2.msi
Even though the Server doesn't display a user interface, the installer will still be able to display its GUI as will Retrospect when it is opened.