This problem occurs if FreeMIDI Drivers have been removed from the FreeMIDI Folder in the System Folder. FreeMIDI installs a set of MIDI Drivers into the FreeMIDI Folder which are required for operation. At the very least, do not remove the SCC Driver from this folder. Without the SCC Driver, you will not see visible serial ports in the FreeMIDI Preferences, nor will you see interface selections from FreeMIDI's Update Interfaces window (Configuration menu).