When installing Little Green Button, the installer will attempt to put in place the necessary Firewall Rules.
If this fails for any reason, a warning is displayed
Adding the extra parameter SKIPFIREWALLRULES=1 to the command line e.g.
msiexec /i lgbsetup-3.17.9067.msi /qn SKIPFIREWALLRULES=1
will direct the installer to avoid any attempts to modify the Firewall itself. Therefore the warning won't occur.
Further .msi launch parameters can be found in Deployment To Multiple Workstations.