If anyone out there is still using the File Transporter system, there’s a compatibility issue with High Sierra. The last version available via the official update channel is 4.2.12, but there’s a patch for version 4.2.18 available from their support site. This restores access to the Transporter Library.
This issue reminded me that support for this system ended in September, 2017, so I’m on borrowed time. I just upgraded to the 2TB storage plan on iCloud, so I may test migrating the data I have on the File Transporter into iCloud… but that seems risky.